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Hello everyone. As you can see, I never post because the wonderful search feature assists me in finding the answers to my problems. I cannot find any solutions to this particular idle surge issue due to posts being started but never finished with posted resolutions. Therefore, I am determined to finish this thread all the way through with a posted resolution from the help of the knowledgeable. Thank you in advance to all that post their suggestions/advice.
Background:
'91 Camaro RS: 350 TBI/T5 Transmission (Originally a 305 TBI; was seized doing donuts around a Jetta, in high school.)
Throttle body and all accessories were used from the 305.
305 ran like a top when I purchased the Camaro. 350 ran just as smooth after the swap.
Manual cooling fan was installed before the purchase.
Camaro sat for 2 years after the swap. (Left for basic training)
Problem:
At a cold start-up, the idle surges between 500-2,500 RPM's and wants to die (and is occasionally successful).
At warm-up, the idle continues to surge within the same RPM range listed above. After driving around, the idle will stop surging and will sit smoothly at 1,000 RPM. If I shut the engine off for even a second, the idle will surge again.
When the fan is off, the idle does not surge as much. When I turn the fan on, the surge gets worse. (About the same range as listed above)
Findings/Actions:
Knock sensor, coolant temperature sensor, and idle air control (IAC) valve have been replaced. (Surge still occurring)
Vacuum hoses have been sprayed with carb cleaner, again and again, returning no results of a leak.
While engine was running, throttle positioning sensor (TPS) wiring was pulled. Service engine soon (SES) light came on and idle stopped surging. RPM's sat steady at 2,000. Shut off engine, reconnected wiring, restarted, surge returned with no SES light displayed.
While engine was running, IAC valve wiring was disconnected and no SES light was displayed nor was there a change in the idle surge. IAC valve wiring was tested with a meter and power was coming through the two positive prongs in the connector. The two grounds were functioning properly as well. The IAC was replaced and the idle surge returned.
While engine was running, the manifold absolute pressure (MAP) sensor wiring was disconnected. SES light came on and RPM's sat at about 1,150-1,200 RPM's with no fluctuation. Shut off engine, reconnected MAP wiring, restarted engine, idle surge returned with no SES light displayed. (Another person on these forums ran into this issue but did not end up with successful results after replacing MAP sensor)
EGR valve diaphragm appears to be functioning properly.
No codes are being pulled during normal operation of the engine. (No tampering of any sort)
Does anyone have any suggestions as to what else should be looked at or tested? Thank you again in advance for any advice!
Have you tried checking TPS calibration? There is a post about that around on here. I know it needs to read about .5V with throttle closed. Aside from MAP and TPS, those are the only things that should affect how much fuel is added at idle. IAC would be your air compensation since a tiny amount gets around throttle blades. Unless it's a lean surge from plugged fuel filter or a bad pump, your best bet is going to be to check or replace one of those 3 sensors.
You should probably go through and trace out all vacuum lines and look for leaks while your at it. That could throw off the MAP and it will add fuel to increase RPM and bring up vacuum.
How did you account for the additional needed fuel(305 to 350)?
Key on engine off do you get a CE blink then steady on? that shows it in running off the .bin rather than limp mode.
did you datalog the surge event? It may be idle speed is too low and stall saver is kicking in. I would raise the idle a tad with TSS to see if that stops surging.
I assume fuel filter is fresh and fuel pressure is steady(idle).
I was having a similar problem for the last year since I swapped my 305 tbi to a slightly modified 355 tbi. Idle would go up and down whether it was in park or drive, warm or cold.....but not all the time, just most of it. No trouble codes or check engine light ever came on. Found out through this site that with the engine swap I needed to change the ESC (electronic spark control) module. They are not the same from a 305 to a 350. Put that in last Sunday and the car has never run so smooth. Long story short, just wondering if you had replaced this when you did your swap. Mine didn't start right away either btw.
I know it's been a while since I've posted but I have not given up! I ran into an annoying VATS problem that was a higher priority. Couldn't get the car started... I will be diagnosing this weekend.
Originally Posted by TZFBird
Have you tried checking TPS calibration? There is a post about that around on here. I know it needs to read about .5V with throttle closed. Aside from MAP and TPS, those are the only things that should affect how much fuel is added at idle. IAC would be your air compensation since a tiny amount gets around throttle blades. Unless it's a lean surge from plugged fuel filter or a bad pump, your best bet is going to be to check or replace one of those 3 sensors.
You should probably go through and trace out all vacuum lines and look for leaks while your at it. That could throw off the MAP and it will add fuel to increase RPM and bring up vacuum.
I haven't checked the calibration on the TPS. I will inspect it and post results. Thanks TZFBird.
Originally Posted by Ronny
How did you account for the additional needed fuel(305 to 350)?
Key on engine off do you get a CE blink then steady on? that shows it in running off the .bin rather than limp mode.
did you datalog the surge event? It may be idle speed is too low and stall saver is kicking in. I would raise the idle a tad with TSS to see if that stops surging.
I assume fuel filter is fresh and fuel pressure is steady(idle).
After the swap, nothing was changed. I used all the top end parts from the 305. The engine ran great before I left, and it sat for about 2 years.
The SES light does not blink. It is steady on from initial turn.
I'm not sure how to datalog the surge event. TSS? You mean TPS?
The fuel filter had been replaced less than 5,000 miles before it sat. And I have not yet checked fuel pressure. I will run a test this weekend and post results. Thanks Ronny.
Originally Posted by jingles89
I was having a similar problem for the last year since I swapped my 305 tbi to a slightly modified 355 tbi. Idle would go up and down whether it was in park or drive, warm or cold.....but not all the time, just most of it. No trouble codes or check engine light ever came on. Found out through this site that with the engine swap I needed to change the ESC (electronic spark control) module. They are not the same from a 305 to a 350. Put that in last Sunday and the car has never run so smooth. Long story short, just wondering if you had replaced this when you did your swap. Mine didn't start right away either btw.
My surging idle is similar except for the fact that it does not surge when the engine is under load. I have not changed the ESC module from the 305 to the 350. The car ran great for months after the swap. After it sat, the surge began. Mine started up right away as well. Glad to hear you found the solution though!
While driving home from work, I didn't stomp on the gas pedal but I stepped on it a little harder than usual and the SES light came on after I let off. The engine felt like it had no *****. It was chugging whenever I increased speed. I pulled over, restarted the car, and the light was gone and power had returned.
As soon as I returned home, I jumped the ALDL connector and pulled nothing but the assumed 12. WTF? As posted in the 1st post, the knock sensor was replaced. I know that can retard the timing and kick on the SES light. Any ideas?
When engine runs off chip you get with ign on engine off that blink of CE. Solid is limp mode. I suspect you have a .bin failure or a ECU failure but intermittant. Did you ever remove ECU from vehicle? I had that issue when I swapped ECUs. Mine was not plugged/seated in 100% and I had same issue. Same issue I had on chip when I used a socket that made chip easily removable and unseated on hard bump. You may want to disconnect battery and reseat chip as well as ECU. Check for dirty connection.
The engine felt like it had no *****. It was chugging whenever I increased speed. I pulled over, restarted the car, and the light was gone and power had returned.
That sounds exactly like what mine did when when my wire fell off of my water temp sending unit. You said you replaced yours, maybe the wire is messed up down deep?
When engine runs off chip you get with ign on engine off that blink of CE. Solid is limp mode. I suspect you have a .bin failure or a ECU failure but intermittant. Did you ever remove ECU from vehicle? I had that issue when I swapped ECUs. Mine was not plugged/seated in 100% and I had same issue. Same issue I had on chip when I used a socket that made chip easily removable and unseated on hard bump. You may want to disconnect battery and reseat chip as well as ECU. Check for dirty connection.
Good news! I don't know what I did while checking components but I am no longer running in limp mode. When I turn the key, the SES light blinks once and returns solid. I looked at the ECU today and it looked like no one had ever messed with it. I pulled it anyway and inspected the PROM and electrical connectors and everything checks out visually. Connections were clean and seated properly. Thanks for the help Ronny, if you have any other ideas, let me know.
Originally Posted by Zerocyde
That sounds exactly like what mine did when when my wire fell off of my water temp sending unit. You said you replaced yours, maybe the wire is messed up down deep?
You had an erratic idle from that? Did you get an SES light? I have replaced the coolant temp sensor and everything checks out. Thanks Zerocyde.
I just got my car running after it sat for one year. I ended up having to replace the distributor and the coil. It fired right up and ran good, but... It would surge. Not all the time, just most of it. Never under load, but most of it's time at idle. Sometimes I could turn the car off and back on, and it would stop. Sometimes it would be fine but if I turned it off, it would come back when I restarted it. I checked the IAC, TPS, and MAP the same as you, to the same effect. Seems to be the EXACT same problem you have. I'm going to be following this thread and chiming in with any ideas I get about it on my side. After I play with it some more, hopefully one of us finds something and can help the other.
But... As of an hour ago I went out to start it and pick up my fiance from work, and the Silverado next to me is running with nobody in it. I think that's strange. Then I get in my car to start it and I don't hear the pump kick on with key on... That's because the Silverado next to me is not running, that's MY fuel pump that was running. And now my battery is dead. :/ I unhooked the battery for 20 minutes then hooked it back up, and the pump was STILL constantly on. Seems like I could hear a rushing sound (like something under pressure) when I was under the hood, it was at the back of the intake, and very loud. It was odd.
So my battery is dead and fuel pump is constantly on... I'm charging the battery tonight and will troubleshoot tommorow.
My car is an all original V6 with a manual btw... Which leads me to believe your swap has nothing to do with it.
fresh motor in (bored out the stock 5.7).
It did this BEFORE the motor getting rebuilt, and it still does. the whole "turn the car off then back on" thing also works for me.
it idles funny, but it isn't only at idle. Sometimes it's as if it's running on fewer cylinders...then pumping the pedal a bit get her powering up again...it's strange...
Has anyone figured this out? Mine has been doing this for what seems like forever, even before the 350 swap.
I just replaced the fuel pump today and it still does it, but that's not why I changed the pump. The TPS, MAP, IAC, Temp, Knock Sensor and some vacuum lines were changed. The vacuum lines were recent. The computer has been swapped with a spare, but the ESC is still for the 305 and the other ignition components have been replaced. It also has a fresh filter. The SES will sometimes come on and then go back off after driving for awhile and may come back on again. That's weird.
I've been working like hell to get this thing back in working order and am getting close. My transmission problems will have to be addressed next.
The car smooths out after it's warmed up, but it is a very cold hearted TBI.
I rebuilt the throttle body today and put a new FPR diaphragm in (whole kit is only $26) and the injectors looked very good and the screens were nice and clean, but I replaced the screens anyway. I used a 6 volt homemade battery thing (made with AA's) to open the injectors while back flushing with carb cleaner after the screens were off.
There are two gaskets given in the kit. One is solid and one has a passage between both sides and the existing was the open passage gasket. After examining the TB, I noticed that there are already passages for air to move to each side and they were routed in a specific manner, which logically said to use the solid one.
It was almost 3 hours after shutting the car down, (I very much took my time) but I unplugged the coil wire and had my cousin crank it to make there were no leaks and the injectors were spraying. Everything seemed ok, so I put the coil wire back on, had my cousin turn it over and it fired right up! No surging!!! Drove it about 10 miles with no trouble and then parked it. I need to get another hose for the PCV valve though. It is leaking something terrible and idle is high at just above 2k, but it ran smoother than it has in 8 years!!!
The old FPR diaphragm looked horrible.
I have to wonder why they include that gasket, unless it is for someone who also has a spacer?
I am going to get another PCV hose tomorrow and see how it goes. I've already replaced other hard and cracked lines, so I guess I should have examined this one more closely. Well today I did!
So if anyone used the gasket with the space in between, that could very well be a problem. I didn't even have to let the car warm up like I usually do!!!
It would always surge and give me a hard time after the 350 swap until warm.
The intake was still a little of hot when I put the TB back on, so the first start tomorrow will tell me. After I plug the PCV line of course.
So now the entire fuel system has been rebuilt, which also includes a fuel pump relay that I didn't need. The Bosch fuel pump seems to be working very well and yep, the filter was also replaced not long before the pump.
I had the same problem. It would not stop surging unless you unplug the Tps and or the MAP. Give it some pedal and it felt fine but it would not idle at all. After a week it would only start with starting fluid and backfire through the tbi sometimes and when it started it would not have any power at all when you step on it.
I replaced the Tps since it was failing, not completely but it would hang up and loose the rpm for half a second then come back. Map was fine but I went and got a replacement from a yard which I ended up putting back the original. The culprit was the FP. I replaced it with a beefier pump and now it starts up like a champ and feels better than ever.
Here is the things I did which might of contributed but in the end the FP was definitely bad and so was the rubber line that connects the pump to the assembly.
Anyways here is the things I did.
Check Vacuum lines.
Replaced CTS.
Replaced Fuel Filter.
Checked Fuel lines.
Tested EGR and Cleaned it.
Rebuilt TBI with Gasket pack from Oreilly (Part # 10902, Included FPR Gaskets)
Replaced Rotor and Cap
Replaced TPS
Replaced Fuel Pump with a working one from a 95 Chevrolet Blazer and Installed new Strainer.
I got my sensors from a local yard. They sold em for $1 each with 30 day warranty if they dont work. The Map sensor I got for free from a family member but the original one was working fine and the one given to me would cause me weird small idle jumps and would throw out the SES light when getting warmed up.
Shes running now, it was a pain in the *** to get the tank out, I think my total for this was right around $100. Not bad in the end. My father had a brand new pump in the Garage but it was too late and the tank was already installed.
One thing I am investing into is a Fuel pressure tester that works with our cars or find a workable gauge system. Trust me, knowing if its a fuel problem is very time saving and would get the whole ''God dammit if I have to drop the tank.....'' thought out of your mind will help you alot.
Last edited by Carlos773; Jul 8, 2010 at 02:22 PM.
I am quite amazed at how well my car was running today. I've pretty much rebuild the fuel system from the pump to the injectors; not counting the fuel lines of course.
First start of the day it ran without the surging and with minimal (but still present) cold heartedness that I usually have. I’ll check main tuneup items now and will also be switching back to regular non fancy stock AC/Delco Plugs. It has Denso plugs in it now.
Is it best to get plugs for a 350 or 305 since the heads are still 305? I always get them for a 5.7L since that’s what the block is.
It is getting much better gas mileage and I am just flabbergasted about that. I'll see how well it’s done the next time I need gas. My trip OD is broke, so I wrote down the mileage on the main OD and will compare. I swear just from watching the gauge that it's getting as good, if not better mileage than my 1993 3.8L Regal did.
Not sure why the car is running cooler now because I know it can't be related to the throttle body (I think) and the transmission seems to be shifting better, although it was only in the 70's here today, but the temp gauge is showing cooler. Just barely touching the top line, one notch down from 220. Was the Throttle Body being screwed up making it run hotter? No, that can't be.
The transmission thing is just puzzling. I drove it roughly another 35-40 miles today and the transmission shifted almost flawlessly. Always into 4th at 45mph, which is just weird because of how it’s been acting lately. I even have another governor coming that I bought for $0.99 on eBay to see if it had anything to do with late shifting, so the TV appears to be correct if it's shifting into 4th when it should now, right? I don't have a clue, but for 99 cents and a few bucks shipping, I don't care. Total is just over $5 and it's complete from top to bottom with a 30 day guarantee and was told any configuration, but I just said it was for my daily driver with everything stock.
Now I have to change the power steering pump and figure out which rod is knocking (after warm) and it's good to go. I was going to drop the pan earlier, but then the fuel pump started going bad and I had to attend to that. It’s been running 8 years with the knock, which is worse when I let up on the pedal, but not so much when I put it in gear.
It’s not getting worse, but the oil pressure has always been over 30 when cold and about 15 when warm and 0 at idle, which makes it sometimes stop running at places like a drive thru because of the oil pressure safety thing I guess. That’s what I’ve heard. No other knocking than just the one rod and it sounds like it’s in front. I know… I’m absolutely crazy, stupid, dumb, idiotic whatever for driving it all this time with it like that, but it’s not getting worse, so…
From my research, I understand that it could be a spun bearing after the rebuild?
It’s not getting worse, but the oil pressure has always been over 30 when cold and about 15 when warm and 0 at idle, which makes it sometimes stop running when stopped at places like the drive thru because of the oil pressure safety thing I guess. That’s what I’ve heard. No other knocking than just the one rod and it sounds like it’s in front. I know… I’m absolutely crazy, stupid, dumb, idiotic whatever for driving it all this time with it like that, but it’s not getting worse, so…
From my research, I understand that it could be a spun bearing after the rebuild?
Im new to third gen world. Just bought a 91 iroc 305 tbi. At cold idle has bad surge and almost dies , then after it warms up runs better but has high idle ands very slight surge driving down road. temp sensor replaced iac replaced and air charger temp sensor replaced to no help. Sounds like rebuilding tbi might be the fix the car only has 112000 on it and sat up on and off. Any other info would help.
Im new to third gen world. Just bought a 91 iroc 305 tbi. At cold idle has bad surge and almost dies , then after it warms up runs better but has high idle ands very slight surge driving down road. temp sensor replaced iac replaced and air charger temp sensor replaced to no help. Sounds like rebuilding tbi might be the fix the car only has 112000 on it and sat up on and off. Any other info would help.
welcome to the club they all seem to surge and there is no one way to fix it.
everyone seems to fix there car different. Mine is doing it now and its killing me. I have replaced everything and nothing changes the surge.
One cause is the vacuum hose under the TPS on the TB (TPI). Mine came loose and did that surging for a min or two before it evened out. It would stutter slightly on accel too. Not sure where the other end goes atm but check that line thoroughly.
One cause is the vacuum hose under the TPS on the TB (TPI). Mine came loose and did that surging for a min or two before it evened out. It would stutter slightly on accel too. Not sure where the other end goes atm but check that line thoroughly.
that was one source of my surging I may need to rebalance my tbis again
Has anyone figured this out? Mine has been doing this for what seems like forever, even before the 350 swap.
I just replaced the fuel pump today and it still does it, but that's not why I changed the pump. The TPS, MAP, IAC, Temp, Knock Sensor and some vacuum lines were changed. The vacuum lines were recent. The computer has been swapped with a spare, but the ESC is still for the 305 and the other ignition components have been replaced. It also has a fresh filter. The SES will sometimes come on and then go back off after driving for awhile and may come back on again. That's weird.
I've been working like hell to get this thing back in working order and am getting close. My transmission problems will have to be addressed next.
The car smooths out after it's warmed up, but it is a very cold hearted TBI.
Gunna jump in here change th module in the distribiter I had misfired timing adjusting cause the knock sensor was hearing. And. B. Sure when you change something clear the codes before you try it again. Some of me leaves the batt connected I know. Its a foul practice the ground strap from the frame to the rear of the right head and the one from the same spot up to the cab are a must and check the connections on the fuel pump relay. Try some of those and let me know thanks....
I'm going to document step by step as I try to fix this issue, I've just bought a 1990 Formula 305TBI 5 speed with less than 20k on the clock and it does this same idle surge crap, it's very annoying and the car sometimes dies, I have to keep it revving at the lights so that it doesn't die on me, it surges between 500 and 1k rpm. I am going to go through the system step by step and attempt to fix this nonsense.
The first step I will take is to inspect all the vacuum lines and the EGR valve, that I will do tomorrow (Christmas day) And I'll report back, I have all new filters, TBI rebuild kit and a whack of other new parts on the way, I don't want to make the mistake of just throwing everything on the car and hoping for the best, I will do it step by step until the issue is resolved.... Wish me luck
Okay, so I gave the engine a reasonably good clean (not a perfect detail or anything), here's the before:
And Here's the After:
During the clean I check all of the vacuum hoses and couldn't see anything broken or damaged, there were a bunch of small annoying things like a leaky heater hose, cracked coolant expansion box, missing battery hold down and some random wires that were unplugged for whatever reason. I fixed what I could and focused back on the idle issues. I gave the TBI a little bit of a clean, there was a lot of grime built up all around it and the gasket holding the spacer was falling apart, so I cleaned up all that mess, after a good clean of everything I started the car and it still had the idle issue and a check engine light... Okay, next I popped off the cap of the distributor (Why is it so bloody hard to unscrew these things, bad placement!) and well:
I don't even know how this car was running... This looks like it was pulled from under the sea...
The contacts in the cap were also ridiculous! A good scrubbing, a lot of WD40 later and I put it all back, I started the car and yes it's running better! Still surging but way, way better! It's not trying to die! I'm going to order a new distributor. just replacing the cap and rotor probably isn't enough here, on a side note I got the Service Engine Soon light to bugger off finally (not sure if it'll be back), but I did this by pulling the code which was code 24 (VSS) strange since the speedo works just fine, I crawled under the car and pulled off the connector and cleaned up the huge amount of oil all over everything, reconnected it and it seems to have fixed the issue!
Progress so far:
Checked Vacuum lines - Okay
Reconnected a random brown and black wire that was disconnected (still not sure what it was but it looked like it should be connected, I'll chase it down later)
Checked Rotor and Cap - Completely effed up (will replace)
Messed around with the VSS connection
Result: Car is running better, still surging but not nearly as bad, Service engine light has taken a hike!
I'm going to document step by step as I try to fix this issue
Excellent. You've supplied some good photos, too. Might want to post pics of your mystery wires
Originally Posted by SerpentZA
The first step I will take is to inspect all the vacuum lines and the EGR valve, that I will do tomorrow (Christmas day) And I'll report back, I have all new filters, TBI rebuild kit and a whack of other new parts on the way, I don't want to make the mistake of just throwing everything on the car and hoping for the best, I will do it step by step until the issue is resolved...
Good first steps. The computer can't fix "tune-up" problems like failed rotor, defective cap, worn spark plugs, etc. When you have the plugs out for inspection, might be nice to perform a cranking compression test of all eight. And of course, the EGR is well-known for idle problems if not closing properly.
After that, fuel pressure test.
At some point real soon, you're going to want to connect that car to a REAL scan tool. Codes...sure. The data stream is at least as useful as "codes", and often more useful.
In particular, could be fun to see if it's dropping out of closed-loop at idle, and to determine O2 sensor info, commanded idle speed info, actual idle speed, IAC position, coolant temperature, and MAP sensor data.
Agreed! I still have a long way to go and do plan at some point to figure out the whole data logging and chip burning stuff, I'm planning on investing a significant amount of time and money into this car as it's one of my dream cars (I'll make a proper introduction / story post at some point with a load of photos). Good point on taking photos of the wires, maybe someone here can help me figure out what they are, here's the one I reconnected:
This wire was just unplugged and they look like they're supposed to be plugged in together so I plugged it back in, it's on the passenger side next to the aircon condenser thingie, The AC works beautifully on the car so I'm guessing this has nothing to do with the AC, maybe something to do with emissions? I'd appreciate if anyone knew, also there are two other wires that are unplugged, any clue as to what they could be?:
Tomorrow I'm going to put on the bloody expensive California spec Catalytic converter and see if it passes smog, I'll be driving the car a bit and will be able to see if the Service engine light comes back on, again my goal here is to fix that idle surging issue and parts are starting to arrive, I'll continue to try and do things one by one until it's completely sorted out.
The wire that you re-connected is for computer-controlled timing advance. You disconnect the wire to set initial timing, but it should be re-connected for any actual driving. Without that wire connected, the engine is going to run like shiit, get terrible fuel economy, not idle properly, and have poor power.
Wouldn't surprise me if the computer needs to "re-learn" some fuel and spark control if the wire has been disconnected for a long time. In other words, the more you drive it, the better it gets as the computer re-learns.
Wouldn't you be better-off to NOT install a new Cat until you're sure the engine runs properly? If there's any chance the engine is running rich or lean, or misfiring, you'll destroy that new Cat in short order.
Last edited by Schurkey; Dec 27, 2019 at 04:31 AM.
The wire that you re-connected is for computer-controlled timing advance. You disconnect the wire to set initial timing, but it should be re-connected for any actual driving. Without that wire connected, the engine is going to run like shiit, get terrible fuel economy, not idle properly, and have poor power.
Wouldn't surprise me if the computer needs to "re-learn" some fuel and spark control if the wire has been disconnected for a long time. In other words, the more you drive it, the better it gets as the computer re-learns.
Wouldn't you be better-off to NOT install a new Cat until you're sure the engine runs properly? If there's any chance the engine is running rich or lean, or misfiring, you'll destroy that new Cat in short order.
Thank you for that! It explains a lot! I need to get the car to pass smog as I need to change the plate over to California from Ohio (I bought it sight unseen online and had it shipped here to SoCal) and I need to get it done today or risk being pulled over and fined massively so I'll take your advice and drive the crap out of it this morning through various situations, freeway, mountains, neighbourhoods and stop start traffic conditions and then attempt to install the cat this afternoon and head off to the smog station and warm up the cat on the way (the California spec cat is $350 so trust me I don't want to destroy it but getting properly registered on the road is more of a priority). Passing smog is the main reason why I'm trying to fix this issue but of course I want the car to run perfectly as this will be my daily driver and long term project.
Progress after driving to work:
The idle surging seems to have almost disappeared, it started idling high this morning but self corrected and when I stopped at the office the car idled down to around 500RPM (it seems to slightly surge between 480 and 500) which does seem a little low to me but it hangs around there rather than bouncing between 500 and 1k. The speedo seems to be misreporting speed (either that or the car is way faster than it feels) so I'm not out of the woods yet but this is some real progress!
What I've done so far: Checked Vacuum lines - Okay Reconnected Computer Controlled Timing advance wire (thank you Schurkey) Checked Rotor and Cap - Completely effed up, cleaned it as much as possible and ordered a new one Messed around with the VSS connection (error code 24 no longer present and SES light has gone off) Result:
No longer surges between 500 and 1k RPM, now idles around 480-500rpm when up to temp, still a little rough but hugely improved
Speedo seems to be reporting high (will test with a GPS Speedo app to confirm)
Thank you for that! It explains a lot! I need to get the car to pass smog as I need to change the plate over to California from Ohio (I bought it sight unseen online and had it shipped here to SoCal) and I need to get it done today or risk being pulled over and fined massively so I'll take your advice and drive the crap out of it this morning through various situations, freeway, mountains, neighbourhoods and stop start traffic conditions and then attempt to install the cat this afternoon and head off to the smog station and warm up the cat on the way (the California spec cat is $350 so trust me I don't want to destroy it but getting properly registered on the road is more of a priority). Passing smog is the main reason why I'm trying to fix this issue but of course I want the car to run perfectly as this will be my daily driver and long term project.
Unless you can get an exemption or the car is originally from Cali, you will need to get the correct PROM for your car. The California cars have a different calibration to make them cleaner.
Passed California SMOG with flying colors! (Still in disbelief!)
After installing the Cat I drove for a good hour to heat everything up and of course the exhaust note suffered substantially! frustratingly the idle surge returned again, not as bad as before but now between 500 and 800rpm, I'm confident that the parts I have on order will sort out the issue (and I will post the updates as things improve) As for the speedo, I was correct! It's reporting 80mph when I'm only going 75! This is going to be a frustrating one to chase down I'm sure but that's a topic for a different thread, now I'm sitting in the DMV and the place is packed due to the holidays.... Yay...
I have not given up on this, the idle surge is still an issue, here's what I've done since the last update:
I decided to get the basics out of the way and did a full coolant and oil flush and replace (glad I did as there was rust in the coolant and the oil was watery thin... still all oil but waaay too thin).
Another important discovery is that the Thermostat was rusted open, that explains why the car was running cool and taking forever to get up to temp, so new failsafe thermostat installed:
I used Mobil 1 fully synthetic 5w30 and before anyone gives me **** about that, remember that this engine has less than 20K miles on it, if I see any leaks or seepage I'll change to a fully organic (or use cooking oil or whatever). I also opted for the bog standard Autozone coolant since I wanted to get in the zone!
My new coolant expansion box arrived from JEGS and I'm glad to finally replace the old one as it had been poorly fixed with silicone sealant and was leaking rusty water all over the battery tray (actually caused a lot of rust which I had to clean out with a wire wheel and paint over with rust converter), the old box also had a lot of rusty crud stuck to the walls so I'm glad it's gone!
Why not just replace it? This is America right? I can understand if you're in a foreign country where these parts are unavailable but seriously, just replace this crap if you don't know how to use a proper epoxy!
Waaay better! But let's be honest, a coolant and oil change are probably not going to affect the idle issue although I was secretly hoping that the stuck thermostat was causing the ECM to supply the wrong fuel mixture because of low temp readings...
I also put on new TBI spacer gaskets (above and below), the top one was missing and the bottom one was falling apart and all sorts of bits of crap were being sucked into the engine I imagine, a new FRAM air filter was thrown in too, the old air filter had oil and filth all over it:
I got these gaskets in the TBI rebuild kit which is my last resort, once I've tried everything else I'll re-build the whole thing and probably get new injectors too
And the result was that the car is actually running a bit smoother, better throttle response (not imagined) and a bit nicer to drive! BUT THE IDLE IS STILL BLOODY SURGING!!!
I've just picked up a new IAC from AutoRielly's and that's the next step I'll try, also keep in mind my new distributor has not arrived yet, I also have new spark plug wires and spark plugs on order so that will be a whole thing too when they arrive, but first the IAC and I'll let you know the results.
Okay, so I pulled out the old IAC and it looked gross but serviceable, either way I wanted to eliminate it so I'm putting in the new one!
whilst I was cleaning out the hole with carb cleaner I decided to do a proper vacuum test on the EGR valve since I was there anyway:
The valve held vacuum just fine and it opened when I tested it with the vacuum tester tool, however it got stuck open! Obviously this isn't ideal! I lubed it up with WD40 and pulled it closed with a pair of long nose pliers, I then worked it up and down with the vacuum pump until it was freely opening and closing without any resistance, I don't think this was the issue, but it certainly wasn't helping since it probably either wasn't opening or was opening a bit then getting stuck open... either way I could eliminate that as a potential issue. I cleaned out the air hole thing, it wasn't horrible but was still pretty dirty, here's as clean as it's going to get:
I noticed that one of the wires leading to the IAC had been chafed through so I sorted it out with a little electrical tape:
So, here's everything connected up:
So, initially when I started the car the idle was sitting around 1200rpm (which is normal since the IAC needs to sort its crap out and realise what the heck it's doing) I was excited and then quickly disappointed after a short drive the surging reared its ugly head again. I got annoyed and decided to do some spirited driving to take out my frustrations, so off I went driving around aggressively and cursing out the PO and his inability to do simple maintenance, I finally parked the car and went to do some work, later I went out for another drive and to my surprise, the car seems to idle at an almost steady pace! It's still a little low and idles at 500RPM, occasionally dipping a tiny bit and threatening to stall, but it holds and didn't die once, I took it for an extended jaunt and it seemed to keep up the good work.
Conclusion at this time:
After maintenance, replacing the air filter, breaking the EGR valve loose and replacing the Idle Air Control valve the problem seems to have mostly gone away, I'm not going to call this solved yet as the idle still fluctuates a bit and it's not ideal, I suspect that once the new distributor and plugs and wires are installed that this problem will be solved but until I do all of that I'm going to still call this problem unresolved.
Thought I'd share a picture of it since I finally got to drive it properly without it trying to die and idle surge me to death:
More updates as they happen!
I would have passed on the Failsafe thermostat--it's expensive for no useful reason. And you'll need to repair that wire harness where the insulation has vanished. (The copper inside may now be corroded. If it isn't...it will be.)
I would have passed on the Failsafe thermostat--it's expensive for no useful reason. And you'll need to repair that wire harness where the insulation has vanished. (The copper inside may now be corroded. If it isn't...it will be.)
The thermostat was only a few dollars more than the OE replacement so I thought what the hell, this is my baby so may as well spend more, and yes I agree on the wiring, the plastic clip is also missing (brittle plastic)so I should try and get a new pigtail and then solder and heat shrink in the new connections, all in good time, first I need to ensure that this idle gremlin is taken care of, appreciate the feedback and advice!
Fantastic! Thanks mate, I've just ordered the connector off of your ebay link! I'm really enjoying making this car as good as it can be, I have a lot of plans to do legitimately good mods but first she needs to run right
If you don’t have a small piece of tubing to release the terminals here is a cheap tool. https://www.ebay.com/itm/Delphi-Pack...4AAOSwgotcR13F
make note of the cavity letters on the back of the connector.
the wires need to go in the correct holes in order for the iac to work properly.
A quick update, the new distributor, plugs and plug wires have all arrived, I'll be installing them this week and will have an update on this idle surge issue! In the mean-time I removed the aftermarket alarm system that was causing the car to not start sometimes,
Okay, back to trying to fix this idle issue! Today I replaced all of the spark plugs and that nasty distributor:
The spark plugs all looked to be in good shape but can I say something here... This is one of the worst engines I've ever had to pull plugs from! All that smog crap really gets in the way and I walked away with cuts and scrapes and a whole lot of swearing... I even had to get under the car to remove a few of them, what a bunch of bollocks!
I decided to go with E3 spark plugs this time, I know there's a lot of debate as to if these things are snake-oil or not but you know what? A spark plug is a spark plug and if it makes a spark I'm happy, especially since I don't need to gap these and on the off chance they do actually improve something then why not, I've used them in a Toyota and a Mercedes and they worked just fine, on to the distributor!
This old thing is rough, I really don't know how it was still working.. but getting it off was a nightmare!!! The hold down bolt was over tightened and wouldn't budge! I had to take off the coil and the throttle cable bracket just so that I could actually get a wrench on it that was big enough to give me enough leverage to almost burst a blood vessel breaking it free!
What a stupid design! you can't even get a socket on that bolt because of that plate overhang... Not fun!
Some sort of wasp nest... and although it was rough up top, the gear was in almost perfect shape... I had to really get aggressive sand off the remains of the gasket that had baked into the intake manifold and had become one with the steel... But since I've got all these components out of the way, it's a good chance to clean things up a bit and give it a little bit of paint:
Now time for the new distributor and time to reconnect the wires (I do have new wires but I was done with this crap for the day, those plugs really took it out of me!).
After installing everything and making sure the rotor was lined up the same as before, I got out my cheap timing light and after the engine had warmed up, disconnected that electronic timing wire thing and set the timing to "0" degrees (between that big V) since that seems to be what most people say is good for this engine:
My initial test drive resulted in the surging coming back with a vengeance at first (I'm guessing the computer is working out what all this new crap is), but overall the throttle response was better, it was easier to start and the car ran way better than before, it also seemed to calm down and come to a solid idle by the time I got home, this needs to be confirmed tomorrow when I drive to work, but this problem may actually, finally be resolved! (I'll only call it resolved if the tachometer doesn't even move a tiny bit tomorrow at idle).
Let's hope this is the end of it (I somehow doubt it)...
Like yourself and many others on this forum to include myself we’ve swapped our tired 305’s with 350’s. Like many suggested esc modules with knock sensors need to be replaced along with bigger injectors and a different tune. After reading this post and having recently completed this fix myself I wanted to share as it was easy and fixed a lot of my problems.
The climate control switch witch operates off of engine vacuum and the selector switch fails and seems to be a common problem/engineering flaw creating a vacuum leak. I’ve attached a photo of the part that fails. This is definitely worth looking into:
Like yourself and many others on this forum to include myself we’ve swapped our tired 305’s with 350’s. Like many suggested esc modules with knock sensors need to be replaced along with bigger injectors and a different tune. After reading this post and having recently completed this fix myself I wanted to share as it was easy and fixed a lot of my problems.
The climate control switch witch operates off of engine vacuum and the selector switch fails and seems to be a common problem/engineering flaw creating a vacuum leak. I’ve attached a photo of the part that fails. This is definitely worth looking into:
Okay, so finally after driving to and from work for the last couple of weeks I can say that the idle surge is now completely gone!
She idles at 500RPM and no longer surges, in the morning she'll start up and idle around 1k or 1200rpm until it warms up and then goes to 500, it's a pretty smooth idle (could be better with some more timing adjustment maybe) but it's solid and doesn't try to die or anything.
I wish I could say it was just one thing that fixed this issue, but I saw actual improvements with each and every step I took running down this issue, it's absolutely a combination of replacing and fixing all of these items that finally resolved the issue, I hope this helps other people track down this very annoying issue, I now have a whole whack of new issues to deal with and I'll start new threads for each, but she just rolled over to 20k miles today (I actually think this is BS and that the speedo was just disconnected for a few years since the engine is showing a lot of wear for a supposedly 20k mile engine) but whatever, I can still brag that my formula has just 20k on the clock!
at 30 mph around town i had to basically hold my foot on the brake otherwise i would be speeding .....what fixed it was my fans didnt turn on and she over heated ,idles nicely,no surging ,also read on hear about how he got annoyed and he gassed it ,i remember the old days where a tune up was the mechanic taking the car for a thrash down the local flying mile ,im not a climate denier but we own a v8 and we cant just putt around we got give them some jandle,lead foot,some gas,drive it like ya stole it, ya dont have to speed but get there as quick as you can ,,,,,yeeee Haaa
xkAAOSwJ3Rb~IHb
