Got my low milage IROC on the street again last week after spending last summer replacing/fixing everything. Passed emissions dyno test with flying colors. Engine all stock and was running great. Now it's started the idle surge thing. It acts like it wants to die when stopping, then surges. The computer is obviously hunting for something it cant find when in closed loop. I see from reading the archives that this problem is quite common and few stories have a happy ending. Hopefully, my experiences here will help others (should I actually solve my problem)

I plugged in my moates.net data thingy this morning and started the car and let it warm up while watching the data. My BLM (learn) value is sitting at 108 after warming up for a few minutes, and it hasn't even started surging yet.

My car still has the original plug wires on it and I know that they need replacing since they misfire like mad when they get wet. I think I have one wire that is arcing somewhere once the engine heat really builds up. I think that's why it isn't surging this morning, even though it's in closed loop mode. I have to take it out and drive it a while before it starts really acting up.

Does it make sense that a single cylinder misfire would cause the block learn value to drop to 108?

 

A 108 BLM value would indicate that the ECM is trying to compensate for a rich condition (O2 correction, which is why your surging), so ask yourself what exactly happens with the fuel excess once that exhaust valve opens if one of more cylinders are misfiring....

 

Well, that's what I was thinking. The unburnt fuel "looks" like a rich condition so the ECM pulls fuel. I logged it last spring when I first got the engine running again (new fuel tank and pump). At that time it was adding fuel (BLM in low 130s). I notice now that my IAC is backed out pretty far (count of like 150 when it used to be 30-40ish once warm).

I've done allot of work on this car, but changing plugs and wires looks like a real pain. It's still sporting the factory 7mm Packard numbered wires. I drove the car about 50 miles last night and once I got home (runs good on the road) it was really acting up and actually trying to die at stop signs. It's kinda intriguing how quickly this "symptom" has gotten worse. It was running great after the inspection/dyno, but after a few dozen miles of putting around houston it started feeling like it had a slight regular missfire at idle. After driving it a couple more times, it started the surge crap and I can definitely feel a weak or dead cylinder when it's doing it.

AIUI, a BLM of 108 means that the ECM is pulling 25% of the fuel. That leaves me a bit curious whether the misfire is the actual problem or only another symptom. It definitely feels like a single cylinder, but it doesn't seem to miss when the engine is cold. It doesn't seem to be missing when you stomp it either. Pulling so much fuel due to a bad O2 reading could also lead to a single cylinder missing IMO.

I can see how frustrating this problem could be. The archives indicate some people "solved" it by getting rid of their cars or converting to carb. I'll be doing neither.

Everyone that owns a third gen needs to also own an ALDL reader and a copy of tunerpro-rt.

 

I have a '89 GTA w/ 350. It has been doing the same thing and it will not start when hot. Module and other ign. parts have been replaced with no luck. I feel your pain.

 

That more than likely sounds like your fuel injector....

 

It can honestly be a number of things. The Block Learn Muliplier has a range of 105 to 150, but even if the value reaches close to one of these limits, the ECM can still average close to stoichiometric with the help of the Integrator. Once the corner of an individual cell is met though, with no further adjustment being possible, this will usually point toward a bad sensor, or possibly a problem with the calibration, with the obvious already being checked....

 

OMG, changing plugs and wires was every bit as hard as I expected. Now that I know how to do it, it will be easier next time. I tried running the wires just like the factory, but the passenger's side was impossible to get exactly the same. New wires and plugs; still no worky right. Developes a hard miss at idle after it warms up and goes into closed loop. Seems to smooth out if you keep the RPMS up. I picked up a cap and rotor while I was testing the plugs and wires. To fully illustrate my incompetence by randomly throwing money at it, I also bought an O2 sensor. Waiting for it to cool down a bit so I can install the new parts. ;-)

PS: I didn't reset the ECM after installing the new plugs and wires, but I figured the BLM would automatically climb back up. It didn't, it still wants to run the BLM arount 108 and the INT at 128ish.

 

Put in new cap and rotor, still broke. The reluctor is really rusty, is that a big problem? Once it gets good and warm, it seems to be missing on one cylinder real hard at idle. Seems to smooth out when you get back on the road though, too weird.... Haven't determined the exact cylinder yet, but I have a suspicion that it is the #5. I ohmed my injectors (cold) and found that the #5 cylinder was at 6 Ohms, the rest were all 16.5-16.7 Ohms. Would a flakey injector explain this behavior? Getting hot and shutting down, but starting to work again when it cools back down a little.

The only problem I have now is that none of this seems to explain the BLM of 108 (ECM detecting rich condition from O2 sensor). UNLESS: Maybe the injector is spraying a little bit of fuel when it is acting up, but so lean that none of the fuel burns when it sparks (no knocking)and then the O2 sensor picks up on that fuel when it gets dumped into the exhaust. Is that plausable? It runs beautifully when all cylinders are hitting. The plugs all look good, including #5. I was getting ready to buy a distributor, but I'm thinking I really need a set of Bosch Type III fuel injectors from FIC.

 

I ordered injectors, Bosch III's, yesterday. Should be here tomorrow. My ohm readings were all over the board. The lowest was a 5.5. Only 2 were in the 16's. I was told my 5.5 was shorting out and not completing the circuit, which, from what I understood, will shut down 1 bank of injectors. Mine idled beautiful in open loop and erratically when in closed loop and would not restart till it cooled off. I hope this info helps and I will post results after the injector swap. Bryan

 

I haven't had any restart problems and it hasn't actually died at a light yet, just close. I put my old dizzy back in and hooked it all up, started and idled great. After it got hot, the #5 injector Ohmed out at 16.7 (was 6 when cold) just like the others. (rolls eyes) Listening thru the stethoscope it was clicking like it should. Sounded like the rest. OTOH, when it was running rough I could pull the injector plug or spark plug wire on that cylinder and almost no difference in the idle quality. I'm going to order some injectors I think.

 

Took the car out for a good heat soak yesterday. Ran fairly decently, got a little rough when it got hot, but not really a dead cylinder type miss. Maybe the injectors are cleaning up a bit the more I drive it. Stopped at the convenience store, came out and no start. :-O It would spin over like it was trying to start, but wouldn't take off. Started thinking to myself, ahhhh it is the ignition. Found that I could get it to start if I gave it some throttle, but it would quickly die. I then started it again, but kept pumping the pedal and it ran like total crap for a few seconds then the SES light came on. After that it ran, but really poorly. Limped home and hooked up the moates logger and fired up tunerpro. WTF, coolant temp is -39F. Turns out my CTS died while sitting at the convenience store. Pulled the plug and did the tests, it's definitely the sensor. How weird is that? I mean I know the sensor is 20years old, but why should it die? The one in my '66 GMC pickup works fine and it's the original. Seems like the cap/rotor/plugs/wires did help some. No surging until the SES light came on. Off to get a new sensor, and get back to the original problem of running poorly when hot.

 

CTS changed, man that was too easy. No SES light now, will take it out for a test drive and data logging later. I'm going to swap the O2 sensor first since it's so old.

 

Didn't swap the O2 sensor yet, but I took a long drive in it. Ran great the whole time.... until I parked it for about an hour. Came out, fired it up and it had a hard miss in one cylinder, wtf? Drove it a few miles, it started acting like it was running out of gas. Couldn't rev it high, bad missing and cutting out. Then it just quit....... Coasted off the road and waited an hour and a half for it to cool down since it refused to start. Finally, it fired up, and I was able to drive about 15 minutes with it acting up and then it quit again. I'm thinking this has to be an ignition problem, but I don't understand why the ignition would apparently turn off one cylinder before shutting down completely. Since my reluctor is rusty, I'm just going to replace the entire distributor and not just the module. Does this sound sensible?

 

Installed a module and made it home, but engine would still miss hard when it heated up in traffic. Turned off car, waited a few minutes and tried restarting. Nope, not right now. Wait an hour and a half, fires up. Wait til morning, runs like a top. Put a whole "new" (reman cardone) dist in and even set the timing which was curious. The timing mark was visible near the top of the tab even before unplugging the ESC connector. Is that normal? I expected allot more advance at idle in park.

Cleared codes and took car for a ride. Ran great til it got warm and started missing. Took it home and plugged in the ALDL thingy and the BLM is 119 at idle. Revving engine to 2500 seems to smooth it out and BLM moves to 128ish. Shut it off hot and let it soak for a few minutes. You guessed it, no start. WTF???????? It can't possibly be the module, pickup, reluctor, dist, plugs, cap, rotor, wires. I put an MSD coil on it last spring, has a whole 150 miles on it. I did try just plugging my original working coil in, but still no start. When cranking, it spins fast, almost like it's getting some fuel and spark, just not enough. All log data looks reasonable as far as I can tell.

When it's running rough, I can unplug the injector that Ohmed low when cold, it seems to be the rough cylinder since it has the least effect. I tried unplugging each wire at the cap. Each one gave me a reassuring shock when that cylinder was firing, so I'm pretty sure the sparks are fine..... they must be by now.

When injectors get hot, can they stick open? Or do they typically just stop firing.

 

Progress finally. Went outside to lock things up for the night and decided to mess with it. Tried starting, no dice still too warm. Unplugged the #5 injector (Ohms low when cold, normal when hot, not sure right now). Crank it, starts right up and idles. Doesn't want to take throttle though. Plug the #5 injector in and the engine immediately dies. I've got injector problems or ECM driver problems. Seems to be the injectors since the engine temp seems to be what determines whether it will run or not. Come on, someone speak up. ;-) Sorta makes sense now. A spraying injector is much cooler than one that is just sitting in a hot engine. Romping on the throttle when the engine is starting to miss would make it smooth right out, but putting and idling makes it miss. Get it too hot and the injector(s) is aparently shorting out, drawing lots of current, and shutting down the ECM drivers. I guess that's not enough to blow fuses though. I must have at least one other injector that checks good cold, but craps out when it gets too hot.

 

My vote is for injectors. I had injectors that ohmed from 9.7 all the way to 16.5 ohms. Car would run fine after a cold start. Shut it off after it's warmed up and it wouldn't start for about 8 hours. It would crank and sound like it should start, but wouldn't. Fuel pressure was good. Fuel pump was turning on when I'd turn the key. But no warm start.

New Bosch III's from FIC and immediate difference. Idled better than it did brand new after putting those in.

Any injector that ohms under 12 is dead. And you might as well replace them all as a set because the rest can't be far behind. If your injectors aren't working right, you'll NEVER get a good combustion/smooth operation etc.

 

Thanks for the reply. I'm pretty sure it's got to be injectors now. When it's missing, it's definitely one cylinder acting up. Aparently, as long as it's not hot enough to shut the ECM down, the injector sprays and if you rev it the injector sprays enough to run the BLM back to the middle. At idle, when missing, the ECM thinks it's too rich. Either the injector is flooding the cylinder, or it's depriving the cylinder of too much fuel. I'm thinking it's starving the cylinder at idle since there is no black smoke or rich smell from the exhaust. Plus it's always clicking like it should as long as the engine is running. I have to say, when it's running on all 8 it kicks butt.

 

I changed my injectors out yesterday. Solved my problems... Engine idles smooth, cold to hot and restarts.

 

My 89 Formula has the same syptoms, except for stalling and restarting problems. I want to perform the ohms test on my injectors. I've never done it before, what is the procedure. THANKS!

 

Remove the plug and measure the resistance between the two pins in the injector. Be careful, these are old connectors. Measure them cold and hot and report back what you find.

 

How to ohm check

 

I tested them warm first since I drove the car over to borrow a voltmeter. Its not good results, should I bother with a cold test?

#1 - 10.0
#2 - 13.8
#3 - 17.5
#4 - 12.0
#5 - 9.6
#6 - 8.0
#7 - 17.5
#8 - 18.1

 

No.

 

OK, so heres the real question. How much are 8 good injectors going to cost? I'm laid off and money is tight, but I don't want to put junk in.

 

It's time....http://fuelinjectorconnection.com/sh...&productId=134

 

Thanks, I really wish I read all this before wasting time and money on an EGR valve. Now all that intake has to come back off.

 

Hey Reid Fleming what part of houston do you live in? Im in the northwest 290/BW-8 area.

 

I just ordered a set of Bosch type III's, should be here Friday.

 

Mine is experiencing almost the same symptoms. My Ohm readings on the injectors were find cold but all over the place once heated up. I just ordered some Bosch type III's as well from FIC yesterday. Holler if it helped.

 

Just got mine in the mail today, great packing job on their part. They look good as new, I can't tell that they're rebuilts by looking at them. I called and they gave me the e-bay deal they're running, so with gaskets and priority mail shipping it came in under $200. I'll be putting them in this weekend. Never had the plenum stuff apart before, this will be a new experience.

Q: How low of a thermostat temperature can I run with the stock PROM without problems.

 

OMG, what an ordeal this is. At least I finally got it all apart. Tops of the old multics are rusty. Plenty of crud built up around the top and the fuel rail showing that they must have been leaking some. Done for the night, but I have some questions.

Q1: The fuel rail is not clear coated is it?
Q2: What do I do with all these o-rings that came in the gasket set?

 

The rail is not coated. Polish away. Looks nice when it's done.

If you don't need the o-rings for the injectors just hang onto them "just in case".

 

If these are the ones in the pack? I believe those o rings are for the fuel rail, if it is taken apart. The injectors will have o rings on them.

 

Yep, that's the ones. I was thinkin' they might be for the rails. What to do now? Should I take it all apart and replace them? I didn't really see signs of leaking in the rails. Bought new pressure regulator diaphragm and it came with a pack of tiny o-rings also. Finally getting ready to put it all back together, but I need an EGR gasket that I won't have until tomorrow morning. I can still pressure test it today....hopefully.......

 

I have the same problem you have or had. Did the injectors fix it? Works with stock chip and fp reg?

 

Just a FYI... There were not o rings in that pack for the fuel lines, go figure. I reused my originals and it was fine.

 

I was wondering about that as well, thanks for bringing it up; I won't bother looking for any. Maybe the ones in the pressure regulator pack are them???

I had a really hard time with that stupid fuel line bracket bolt and the fuel lines running thru the alternator mounting. I got the line connections loose easy enough, but they were in the way of trying to get the bracket on the fuel rail loose from the block. Who would design such a thing....

Anyone else have trouble getting the factory gasket residue off? It's like they glued the gaskets on both sides for the runners.

 

I disconnected my fuel lines at the flex lines, seemed a little easier, just had removed the serp belt.
Be careful not to disfigure the mating surfaces of these aluminum parts. I would use a solvent and not sand off the residue.

 

Sorry, reread your last post. Sounds like you did disconnect at the flex line? Did you remove the alt.? I took everything out of the way; alternator, air pump, air lines etc. I cleaned all parts plus resprayed misc. brackets satin black. Rustoleum satin black rattle can, is a near perfect match.

 

The new gaskets look pretty thick compared to the originals. Can/should I coat them with anything? I still have to drill out a couple of those plastic gasket pegs that are stuck in the intake. I used a whole can of gasket remover and there is still some tiny remnants stuck on the aluminum. I admit I carefully used a D/A sander and fine paper to take down the thickest stuff, think I hurt anything? I swear they were glued in with that indian head stuff. I've never seen anything that hard to get off. This car has never been apart since I took delivery at 21 miles on the ODO.

 

I unhooked them at the fuel rail. Once I finally removed the alt during reinstall it was easy to get back together. Just tested for leaks, had one at the pressure gauge. LOL. I still have a slow leakdown like before. I still have check if it's the pump or the regulator.

Haven't installed the new regulator diaphragm yet. Just noticed the funky TORX that needs a bit with a hole in. sheesh..... I'll change it before I put the runners back on.

Cleaned the intake and polished on the runners and plenum. Polished the fuel rail some, it should at least look better if it doesn't run better.

 

OMG, it's done. Everything is back together except the AIR diverter and pipe. It didn't start the first couple of trys so I was kinda worried. I checked everything and didn't find anything wrong so I tried again and this time it started firing and then it took off. A little rough for the first couple of seconds then it smoothed out. I let it warm up at idle and it seems to be running perfectly and no water leaks even. I just got out of the shower and I'm taking it for a ride now. Wish me luck. 180 stat and coolant bypass also installed.

 

Awesome, no more hard missing. No more won't start when heat soaked. No more shutting itself off when driving. One lousy injector and I replaced my whole ignition system practically. The car now runs just as good if not better than it did when new. Great throttle response. It will squall the tires with a 25MPH kickdown on concrete. I'm happy. :-)

 

Good to hear everything worked out.. I was wondering, what gaskets were included with everything and does it come with all the o-rings?

 

The injectors came with their respective o-rings and a kit with runner to base, runner to plenum gaskets and throttle body gaskets. It also came with a bag with a bunch of o-rings that are aparently for the fuel rails in case you completely disassemble it, I didn't this time. I put it thru some good heat soaks and it seems to be fixed now, no more surging either. My idle could be a little smoother, but I really need to run some seafoam and a couple of tanks of gas thru it first. I will say that it seems to have more overall power and the throttle response rocks.

 

Good job! How about a pic or two of the polish job???

 

I got my injectors this morning and spend the day installing them. What a pain but its fixed. Aside from a coolant leak everything seems fine. I let it idle for 10 mins and no surging. Will test drive as soon as the weather clears. And I did have trouble with the fuel line brkt bolt. All i did was remove the little screw the clamps the lines on the other side of the alt and was able to wiggle them out of the way to remove the bolt. But ya, dumb mounting design! Its jobs like this that really make ya love this site. Can u imagine how much a shop would've charged for this?

 

Good deal, did it idle smooth? Once I decided to completely remove the alternator, the fuel bracket got allot easier to manage. I had the most problems with the old gaskets being stuck to the aluminum. Even MEK based gasket remover had a real hard time taking it off.

Poured in a can of seafoam and filled the tank after getting it going again. After about 65 miles of mostly city driving, I still have more than 3/4 tank of fuel and the idle quality seems to be improving. I'm being real critical on the idle quality here, it's more than smooth enough for good drivability. It's as good, if not better, than it was when new. It's just that I'm a really **** perfectionist about things, that's why I spent days doing the swap. Well, that and the incredible houston heat, humidity, and mosquitos.

 

Mine idle smooth at start up, but it always did, it was only surged after it warmed up. it looks like I may be able to test drive today...

 

You can almost see the fuel rail here:
The slightly bigger picture is here: http://i55.photobucket.com/albums/g1...t/DSC01616.jpg
It's far from show quality, but it's cleaner than before. I've got allot of polish work to still do on the A/C system.