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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Hi guys, just started with this problem today, video link attached of some of weird behaviour.
88 Trans am, 5.0 TPI.
I was driving along the highway in heavy traffic (very hot weather too) and the car started spluttering and stalled out, I initially thought I was out of fuel because my gauge doesn't work properly but it started back up and I took the next exit and made it to get fuel and judging by the amount I put in I wasn't out of fuel.
Sitting in the garage carpark I start it and just sit in D and after a few minutes it stalls, I start it right back up and it starts doing what's in the video, rpm dropping and picking up while check engine light flashing on and off, which it didn't do at all before. I didn't want to keep it running doing that so I turned it off.
Driving it to the service station it felt like it had no power, sluggish.
I had noticed earlier on the highway at speed the car kind of felt like it was shaking, not steering related though, hard to explain.
I have suspected for a while that my maf might be bad, could that be the issue and is just at the point where it's almost dead?
It's all stock except for 3" exhaust, southbay bosch 3 injectors, no cat and no smog pump.
Any other info that might be needed to help diagnose just ask me.
https://youtu.be/UqrRxooZCPE
Any help appreciated as always.
Edit: has just done everything outlined above again on me while trying to get home.
I have suspected for a while perhaps the maf was on its way out, hesitation, stumbling, rough starts, misfire I couldn't determine. Any info on that subject as a possibility would be appreciated too.
Vader, I checked for any while on the side of the highway when it stalled the first time and nothing but 12 over and over. I've since unplugged the maf to see how it ran so I'm assuming it probably has a maf code stored now maybe.
It has stalled about 5 or 6 times in total now on the way home. Each time like in the video then off. I let it sit for a bit and try starting and really have to give it some gas and it'll go OK for a while longer then does the video stuff again. Will also idle rough in park and sometimes stall as soon as I put it in drive. Disconnecting the maf seemed to help stop it stalling going into drive but will still eventually stall again while driving and immediately if I bring the car to a complete stop.
I'll go check again for codes, now that I've calmed down a bit and not so p*ssed off at it anymore!
Code 33 sets when flow exceeds 45 gps below 2k rpm and 1/4 throttle.
The ecm has a 5v pull-up on the signal wire. If the signal voltage is 2.2v or higher for 1 second code 33 will throw.
Tuned Performance, code 33 only came up when I disconnected the maf, it has since gone because I reconnected it and disconnected the battery.
The car is still not running properly though, just like in the video. I have no idea where to start to diagnose.
Not sure if it's a fuel issue, It is holding prime, I don't have a working pressure gauge anymore to check the pressure but a few months back when I installed my southbay injectors and my new chip from you, pressure was good.
It starts and runs so it's getting spark.
Air filter is from 2021 but I've done less than 2k miles since then and it gets stored inside a garage so I think that is fine, visually it looks brand new.
I don't have the experience to know what to check next. Any tips much appreciated.
I did adjust the timing recently but just to 8° btdc, in the hopes of a little better throttle response which I got but I wouldn't have thought it would cause a problem like this, just coincidence perhaps ?
Tuned Performance, code 33 only came up when I disconnected the maf, it has since gone because I reconnected it and disconnected the battery.
The car is still not running properly though, just like in the video. I have no idea where to start to diagnose.
Not sure if it's a fuel issue, It is holding prime, I don't have a working pressure gauge anymore to check the pressure but a few months back when I installed my southbay injectors and my new chip from you, pressure was good.
It starts and runs so it's getting spark.
Air filter is from 2021 but I've done less than 2k miles since then and it gets stored inside a garage so I think that is fine, visually it looks brand new.
I don't have the experience to know what to check next. Any tips much appreciated.
I did adjust the timing recently but just to 8° btdc, in the hopes of a little better throttle response which I got but I wouldn't have thought it would cause a problem like this, just coincidence perhaps ?
Any way you can get live data with a scan tool? That would really help point you in the right direction rather than throw parts at it. I wouldn't think 8 BTDC would cause this, that is the same setting mine is at and I have a chip from Tuned as well with no issues.
I see in the video your check engine light is blinking rapidly? Is that with MAF connected etc? I know you mentioned no codes with it plugged in. Almost looks like something is not connected all the way or a ground is loose the way that check engine is flashing so fast. I would check your grounds behind the heads and wiring for ECM, MAF, IAC and TPS.
Any way you can get live data with a scan tool? That would really help point you in the right direction rather than throw parts at it. I wouldn't think 8 BTDC would cause this, that is the same setting mine is at and I have a chip from Tuned as well with no issues.
I see in the video your check engine light is blinking rapidly? Is that with MAF connected etc? I know you mentioned no codes with it plugged in. Almost looks like something is not connected all the way or a ground is loose the way that check engine is flashing so fast. I would check your grounds behind the heads and wiring for ECM, MAF, IAC and TPS.
Unfortunately I have no way of getting live data.
The video is with the maf connected. I'm pretty against throwing parts at it, only reason I have all the new parts I do was part of a big overhaul a few years ago. Ground behind the heads are good, I also just replaced that one last year, the flat braided one as it had snapped. Short of taking all the covering off the worrying looms I'd have to assume they're ok, TPS I checked today, it is functiong fine, .55v, and increases and decreases nicely when I move the little arm on it with the multimeter attached. All the connections on those parts you mentioned appear to be fine.
Check your timing again and make sure your distributor didn't come loose or something. Could also be ICM related.
Get a working fuel pressure tester. They are cheap and readily available. Check fuel pressure.
Check ignition coil and all connections in the ignition and charging systems.
Check all the basics. Often times in the process of just rolling up your sleeves and going through some basic checks, you'll be able to hone in on the root cause.
Check your timing again and make sure your distributor didn't come loose or something. Could also be ICM related.
Get a working fuel pressure tester. They are cheap and readily available. Check fuel pressure.
Check ignition coil and all connections in the ignition and charging systems.
Check all the basics. Often times in the process of just rolling up your sleeves and going through some basic checks, you'll be able to hone in on the root cause.
Ok, I checked all the grounds I know of, replaced one that was a bit crappy looking, sanded the mounting spots a bit and reinstalled.
Timing still on 8btdc, distributor is tight in place.
All ignition/charging system connections appeared fine, I did however buy nice new fancy battery terminals and re did all the terminal ends on positive and negative leads.
Plugged in a fuel pressure tester and things got a little interesting.
Just hooked into the Schrader valve, key on to prime and gets to about 30psi and drops to about 10psi very quick. (Fuel pressure was perfect back in November when I installed new injectors)(fuel pump New in late 2020)
Pinched the top fuel hose and nothing much changed.
Pinched bottom fuel hose and primed and it went all the way to about 60psi and slowly dropped to about 50, guessing just seeping past my vice grips perhaps, then I released the vice grips and it dropped rapidly to around 10psi.
Running the car with the pressure tester connected was jumping a bit around 30psi, very crappy idle.
Am I correct in assuming my fuel pump has packed it in again ?
Ok, I checked all the grounds I know of, replaced one that was a bit crappy looking, sanded the mounting spots a bit and reinstalled.
Timing still on 8btdc, distributor is tight in place.
All ignition/charging system connections appeared fine, I did however buy nice new fancy battery terminals and re did all the terminal ends on positive and negative leads.
Plugged in a fuel pressure tester and things got a little interesting.
Just hooked into the Schrader valve, key on to prime and gets to about 30psi and drops to about 10psi very quick. (Fuel pressure was perfect back in November when I installed new injectors)(fuel pump New in late 2020)
Pinched the top fuel hose and nothing much changed.
Pinched bottom fuel hose and primed and it went all the way to about 60psi and slowly dropped to about 50, guessing just seeping past my vice grips perhaps, then I released the vice grips and it dropped rapidly to around 10psi.
Running the car with the pressure tester connected was jumping a bit around 30psi, very crappy idle.
Am I correct in assuming my fuel pump has packed it in again ?
If you're able to get 60 psi with the return line clamped, the fuel pump is probably not the issue.
Sounds like the fuel pressure regulator is more likely the culprit.
Sounds like the fuel pressure regulator is more likely the culprit.
When they are faulty I've read you get fuel in the vacuum line, or if not fuel present at least smells strongly of fuel however mine does not.
How else would I go about checking it ?
Also, fpr diaphragm was new in late 2020 too, I know parts can just die but thought it worth mentioning.
Put a vacuum pump w/ gauge on the regulator you can see if it holds vacuum.
The only other moving part in there is the spring.
If it tests good, then you might have a leaking or bad injector.
I'll have to get hold of a vacuum pump and try that.
I really don't think it's the injectors, they're new from Southbay, only been in the car a few months, again I know parts do just die, new or not but I'd like to think at least with their reputation injectors wouldn't just go so quick. The pressure drops quicker than it did when I had 2 leaking 35yr old factory injectors.
If your system holds a constant 50 psi with the return line clamped, the injectors can't be leaking too bad or you would continue to lose some pressure.
Even if the FPR is newish, you could still have a problem with it, or a chunk of crap could be holding it open. Sometimes a few cycles of the pump with the return line clamped (creating high system pressure) will dislodge whatever is in there and your FPR will start to work.
I'll hunt up the fuel system check flow chart from the GM Service Manual and post it for you.
I have tried a vacuum pump on the regulator and it seems to be holding pressure. Not really the result I was hoping for.
Can anyone chime in with any other suggestions ?
Being southbay bosch 3's that I have in there now I can't simply lift the rail and the injectors out to see if they're leaking because they don't lock into the rail so I'd have to take them all out and go somewhere to get them tested for leaking so I want to try eliminate everything else before resorting to that.
I have tried a vacuum pump on the regulator and it seems to be holding pressure. Not really the result I was hoping for.
Can anyone chime in with any other suggestions ?
Being southbay bosch 3's that I have in there now I can't simply lift the rail and the injectors out to see if they're leaking because they don't lock into the rail so I'd have to take them all out and go somewhere to get them tested for leaking so I want to try eliminate everything else before resorting to that.
Another idea have you tried a different or new MAF? I hate throwing parts at it but without data scan it’s tough.
My original Bosch MAF would heat soak and not function properly( rich start ups when hot) and a few times did the stalling out similar to what you describe but it was intermittent…if you replace the MAF try for a BSE brand or one that is a reman Bosch with the Hotwire. The Delphi was a good replacement but a member found out recently they had a bad run of them FYI.
Did you re-calibrate the chip for them (even if they're the same advertised flow rate)? Without proper chip recalibration, they've been known to wreak havoc.
The voltage offsets table needs to be updated accordingly for the particular p/n injector you have. Hopefully that p/n has a datasheet.
Another idea have you tried a different or new MAF? I hate throwing parts at it but without data scan it’s tough.
My original Bosch MAF would heat soak and not function properly( rich start ups when hot) and a few times did the stalling out similar to what you describe but it was intermittent…if you replace the MAF try for a BSE brand or one that is a reman Bosch with the Hotwire. The Delphi was a good replacement but a member found out recently they had a bad run of them FYI.
I have one friend with an 86 camaro I could borrow his maf and see how it runs. I've even gone as far as to email bosch Australia to see if they would remanufacture my maf but the refused, said they do it in Germany but only from workshops not individuals. I've heard bad things even about the delphi one, have another friend who's still having issues even with the delphi.
Originally Posted by ULTM8Z
Hmmm... Bosch-III injectors....
Did you re-calibrate the chip for them (even if they're the same advertised flow rate)? Without proper chip recalibration, they've been known to wreak havoc.
The voltage offsets table needs to be updated accordingly for the particular p/n injector you have. Hopefully that p/n has a datasheet.
Yes the car ran terribly with them at first but I had a new chip burned from Tuned Performance from here on the tgo boards specifically for the bosch 3's and the car ran beautifully since November last year till this rubbish randomly started.
Could you guys educate me on the correlation between the possible bad ecu/maf and my lack of fuel pressure ? I'm not knowledgeable enough to know how they can be related.
It looked as if the check engine light was faintly blinking while the engine was running in the video? Not normal unless you have a jumper in the aldl . My thoughts was a bad ecm for it doing that .
Could the fuel filter have anything to do with the low pressure ? Feel like it all happened too suddenly to have just a filter at fault, it was new in 2020 with around 2000 miles on it now.
Could the fuel filter have anything to do with the low pressure ? Feel like it all happened too suddenly to have just a filter at fault, it was new in 2020 with around 2000 miles on it now.
Seems unlikely but if the filter caught some debris or junk in the tank that could definitely cause lower fuel pressure. As easy as a filter change is it’s worth a shot and won’t hurt anything and will eliminate it.
Is that the original tank in there? If so how did it look when you swapped pumps?
As Tuned mentioned the flashing of that CEL in your video really makes me wonder if the ECM is done.
Seems unlikely but if the filter caught some debris or junk in the tank that could definitely cause lower fuel pressure. As easy as a filter change is it’s worth a shot and won’t hurt anything and will eliminate it.
Is that the original tank in there? If so how did it look when you swapped pumps?
As Tuned mentioned the flashing of that CEL in your video really makes me wonder if the ECM is done.
I have my friend coming over sometime this week and we'll swap in his ecu with my chip and see how it goes.
I'll swap the filter as part of my general service which is due soon anyway.
Inside my tank was pristine when I did the pump.
Update.
Swapped my maf with a friend's known working maf, no change, tried his ecm too and again no change, with my chip in his ecm for the bosch 3 injectors.
So I'm back to square one I guess but can now also rule out the ecm and the maf.
Where does one go from here ?
So you have ALL the same symptoms when swapping out the ECM? SES light blinking on and off, low fuel pressure, and stalling/rough running?
1. You know you have a fuel pressure problem. It may or may not be the root of all your current issues, but you know it's not right.
2. You have been provided factory instructions on how to diagnose fuel pressure problems.
3. Pretend that you are starting from scratch and nobody from thirgen.org has given you any advice and you have no other outside help except the service manual. FOLLOW THE DIAGNOSTIC CHART. What does it tell you is wrong with your fuel system?
So you have ALL the same symptoms when swapping out the ECM? SES light blinking on and off, low fuel pressure, and stalling/rough running?
1. You know you have a fuel pressure problem. It may or may not be the root of all your current issues, but you know it's not right.
2. You have been provided factory instructions on how to diagnose fuel pressure problems.
3. Pretend that you are starting from scratch and nobody from thirgen.org has given you any advice and you have no other outside help except the service manual. FOLLOW THE DIAGNOSTIC CHART. What does it tell you is wrong with your fuel system?
This is how I would be proceeding.
Following that it tells me my fuel pressure regulator is my problem however it holds vacuum and no fuel present in the vacuum line so can it still be the culprit for low fuel pressure ?
All symptoms remain with a different ecu.
Also have to add I haven't actually put in a new fuel filter yet but I can get onto that tomorrow and check again.
In regards to one of the system charts, I'm not exactly sure which of the relays is the fuel pump because my car has been converted to rhd so the relays have been moved from the original position, and tbh I have no idea how to apply 12v to it to perform that check. Is it as simple as running a wire from the positive of the battery to the relay?
Based on what I'm reading in this thread, If I were in your shoes I would replace the FPR diaphragm when you replace the fuel filter. They aren't too expensive or difficult to replace.
Just a little update. While I wait for rock auto to send my ac delco diaphragm I thought I'd try something. I still had my old original fpr diaphragm in a box from a few years ago that I replaced as part of a big overhaul on the car so I thought I'd put it back in and see what happened and to my surprise it held pressure, not exactly where it should, primes to just under 40 and running it sits just under 35. Fingers crossed with the new one and swapping in a new fuel filter will solve it.
I checked old receipts and it is possible I bought a non genuine diaphragm, possibly just crap from china so at least this time I made sure it was ac delco, though I'm sure they probably all just come from china these days.
Here are some photos of the diaphragm when I took it out, looks like there is debris on the top piece of it, it was accompanied by a small amount of fuel too but it dried by the time I got my phone out, not sure if that could account for it failing or not. Some of you guys may know.
Alright so I'm calling this one solved. Even though I haven't got a new fpr diaphragm in yet, I'm running an old (possibly original) one that has been sitting in a box of old parts for 2 years and it's running fine again. Primes to 40 and then drops to just under after finishing prime and runs at around 34psi. I'll still put the new one in when it arrives just for the sake of having a new ac delco one in. Still confused that it looked fine as new when I took it out and it still held vacuum. 🤷🏽♂️ In any case, it was obviously bad.
Hi guys, so this problem randomly started up again today. Has been fine since I put the new diaphragm in. Exactly like in the video I linked in the first post. Dash lights flicker on and off then it'll eventually die. Won't stay running more than a minute if that. No idea where to go from here.
No throwing any codes however when I went to check for them I bridged the terminals as normal but after the first flash of 12, no stored codes, second flash of 12 everything just died, the fans stopped and the engine light went out, that's never ever happened to me and as far as I know it'll just keep repeating itself over and over till you turn off the car or the battery dies. Now when I go to check codes it wont even complete the initial first 3x 12 before it all just cuts out.
Anyone have any idea why that is happening?
Could this actually be a fuel pump issue and not the fpr as previously thought ?
As for the power cutting out while reading codes i have zero idea where to even start on that.
Hi guys, so this problem randomly started up again today. Has been fine since I put the new diaphragm in. Exactly like in the video I linked in the first post. Dash lights flicker on and off then it'll eventually die. Won't stay running more than a minute if that. No idea where to go from here.
No throwing any codes however when I went to check for them I bridged the terminals as normal but after the first flash of 12, no stored codes, second flash of 12 everything just died, the fans stopped and the engine light went out, that's never ever happened to me and as far as I know it'll just keep repeating itself over and over till you turn off the car or the battery dies. Now when I go to check codes it wont even complete the initial first 3x 12 before it all just cuts out.
Anyone have any idea why that is happening?
Could this actually be a fuel pump issue and not the fpr as previously thought ?
As for the power cutting out while reading codes i have zero idea where to even start on that.
This sounds more and more like a bad connection or ground and is electrical in nature IMO...also with how intermittent the issue is. I would start at square one and go from there, test the battery(cranking, ripple test for alternator, along with general heath), battery cables, grounds and connections etc. Start with the basics and work from there with an eye on the wiring, a data log would be nice here as well but I think you said you had no access to one.
Remember that TPI cars can act weird when a battery is on its way out or failing. Also, I had a weird intermittent start and die that plagued me for a few years that was caused by a bad Fuel Pump relay connector, the only way I caught it was a data scan when it was happening.
Thanks RedDragon on the tips. Unfortunately, battery is brand new, as I'd run my old one flat too many times forgetting the trunk light was on, also in the last few months I put on new terminals, new battery to body ground, new negative cable from battery to its other mount point on the alternator support bracket, also new ground from right side head to firewall. Done with 2 or 0 awg I can't remember which exactly. Are there other grounds to check ? I was only aware of these 3.
I also keep it on a trickle charge now with the new battery (not even a week old) to avoid it dying sooner than it should.
I know the alternator is only a few thousand miles old, I do have a spare, would it be worth swapping to see any difference you think ?
Thanks RedDragon on the tips. Unfortunately, battery is brand new, as I'd run my old one flat too many times forgetting the trunk light was on, also in the last few months I put on new terminals, new battery to body ground, new negative cable from battery to its other mount point on the alternator support bracket, also new ground from right side head to firewall. Done with 2 or 0 awg I can't remember which exactly. Are there other grounds to check ? I was only aware of these 3.
I also keep it on a trickle charge now with the new battery (not even a week old) to avoid it dying sooner than it should.
I know the alternator is only a few thousand miles old, I do have a spare, would it be worth swapping to see any difference you think ?
The fact that your ECM does not seem to be communicating is troubling, the fans should kick on and flash 12 three times when those terminals are jumped...when that doesn't happen that usually points to a bad ECM or maybe bad wiring/connection to it. I hate to just say replace the ECM as its often not the fault but sometimes it is. I do not have my FSM handy right now so maybe someone else will chime in with other ideas.
I thought I responded to you yesterday but seems it didn't come through, thanks for that link.
What can cause an ecm to just go bad ??
I've been under the dash recently, between the first time this happened and this current time, and all the wiring 'appears' to be in good shape, no corrosion or cracked or broken insulation, that aside I wouldn't know how else to determine the wiring condition.
I really hope it isn't again ICM related as someone in that thread suggested, I'm truly done with replacing them.
I've been reading up on the egr, could it be involved ? I do get a bit of hesitation/stumble and slight misfire when driving, hard cold starts, stalling, things I've read can be attributed to an egr allowing too much flow ? I did clean it a few years ago and it seemed to hold vacuum. I'm sure that is separate to what ever is causing the issue when bridging the diagnostic port though, that really has me stumped.
04-05-2023, 08:22 PM
