Hey again...

Well, I did it! The Fiero is back on the road! I just woke up for now, from a nap after a 28 hour long straight shift working on the car, with no food breaks. I diddnt eat anything for 2 days, and barely drank anything. Wow does it feel good to eat and drink now.

I gave her a test drive, two things I noticed:

1: I press the gas, and it hesitates just for a fraction of a second, before picking up and driving fine (lots of power, more than I remember the stock camshaft giving, brings a smile to my face).

2: I took it on the highway quick, and immediately I started having a bad issue. Suddenly I would lose spark, tach would immediately drop to 0, but then I would have spark again quickly, and the engine will pick right back up where it left off. it happens randomly, and when I went to decelerate it did it a few times, then a nice POW! was heared out of the exhaust, telling me the injectors are still firing, I just lose spark. Could it be my coil power wire I did some wiring on? or maybe a bad pickup coil or ICM? Or maybe an overheating coil? or just a loose connection? it does not lose spark when idling, it moreso happens at speed, or when I demand power from the engine.

and on a side note, I think I got an air bubble in the cooling system, but at work I will lift the rear of the car only way up and burp the system, and fill her up :P

If you guys can lead me in the right direction here, that would be great!

Thanks for your time.

Make sure the wires from the coil to the ICM make a good connection. Wiggle them around while the car is idling.

Try unplugging the Tach Filter to see if it makes the trouble go away.

Preform these tests on the pick up coil and the ignition coil. Again wiggle the pick up coil wires when you make the test



Bring your ICM to a parts store for testing

The ECM gets the crank rotation from the ICM so I'm not sure how the ECM could still be getting a signal that it would use to fire the injectors with if the ignition was failing. I'm thinking that the white wire from the ICM to the coil almost would be the only link that would be past where the ECM gets its signal but would still affect the tach.

[This message has been edited by phonedawgz (edited 08-23-2010).]

quote Originally posted by phonedawgz: Make sure the wires from the coil to the ICM make a good connection. Wiggle them around while the car is idling.

that small wire that goes from the coil to the distributor has broken tabs on it, but I shoved it in the distributor, I wiggled all wires @ the coil, my fix, and distributor while it was idling before I put the car away in the garage at work, and nothing happened, kept idling fine

Well it wouldn't hurt to do the other checks also however:

If the injectors were still running, then the ICM and Pick Up coil would have to be running. The ICM gets it's power from the pink wire from the coil so that one would have to be good. The pick up coil would have to be good. The ICM would have to be good as far as the pick up coil and sending the amplified signal to the ECM. After the engine starts the ECM sends a signal to the ICM and tells it to stop sending the spark signal directly to the coil, but instead the spark signal comes from the ECM.

So if we assume the spark signal gets to the ECM, since the injectors are firing, but some how gets lost before the coil (which is also where the tach picks up its signal) then it could be the ECM, the white wire that runs from the ECM to the ICM with the spark signal on it, the ICM, or the white wire that runs from the ICM to the coil, or possibly the tach filter also on the white wire.

Hmm

Try swapping the ICM. If the ICM is actually dropping the signal out of it only at short times I doubt the parts store's ICM checker would find the trouble.

Check the 4 wire connector to the ICM, specifically the white wire. Check the white wire that plugs into the ECM at pin19

I diddnt do anything and just moved it around today (only have an hour lunch at work to look at it, im planning on getting it home after I fix the brakes), but no stalling or anything, checked the wires without a DVOM, just wiggling, and planning, and looking at the wiring diagram. This never did this before I changed the camshaft out, and I did not break any wires that I know of, I was pretty careful about the whole harness thing. The distributor, however, has been changed with a reman from the Fiero Store, but it might be defective since before the cam swap, I pulled it out, and it spun stiff, I had to lube it. I am going to order a cardone reman from a local parts store and see what it does after that. I would rather that now because the gear on the current distributor is... meh, worn cause of the bad cam, still tight so it doesnt have much play, just one side of the teeth is a bit worse off than the other.

I never road tested with this distributor either, so who knows, it could be this one... and it seems to only cut out while driving and after hot, at idle I can let it sit there for a long while. I am definately going to check grounds, especially ECM grounds... and I just thought of something... I never tightened the bolts to lock the ECM in place, maybe that could be it too. This one is going to stump me probably :P its just a weird issue.

UPDATE BUMP!

Okay, let you know whats going on
I worked on the car on lunch at work today, and it drove really good! I started adjusting the T.V. Cable, and then went to pull it out of the garage... it first diddnt idle right (no idle flare on startup) and put it in gear, it stalled right out. I turned it back on, ran great, again, no idle flare. I rev it once, it just goes and dies without returning to idle. it just kept doing this, I am suspecting an IAC valve or an IAC connection problem. Also, during this time, the loss of spark came into play. I had my scan tool hooked up and watched the ECM inputs, and when I lost spark, I kept the RPM reading inside of the ECM, it did not just lose all RPM reading, I saw the waveform flare down to nothing with the engine slowing down. I put it in base timing mode with the scan tool, it still lost spark (almost on cue). I put it into Limp Home mode, for base timing and base fuel, and still, lost spark on cue when I applied power. it appears to happen more often when I press the gas pedal. is it possible, that the ICM is bad?

I unplugged the Tach filter during testing, it did not change anything. since the RPM signal goes from Pickup Coil - ECM - ICM - Coil - Tach, I am guessing the ICM is bad, since the wiring is all good and there. During camshaft breakin, the Y pipe glowed red hot because I did not have the timing right. Maybe the Y Pipe overheated my ICM?

EDIT: Forgot to say, scanned my ECM during this time, no codes. However before I cleared codes earlier today (before the issues) I had an EGR Code (I have an EGR Blockoff, so that is expected) and a code 42, stating there is an ICM issue. However that can be set during extended cranking, which has happened in the past, so I did not want to jump on the ICM being the problem right away.

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[This message has been edited by Racing_Master (edited 08-26-2010).]

Code 42 and the loss of spark, but not the loss of tach seem VERY related.

The loss of spark without the loss of tach would mean everything is working up to the ECM. That totally confirms your loud pop in you exhaust from before. So the problem could be with anything from ECM - to ICM - to ignition coil. But the code 42 specifically states the ICM saw a problem with the part of the ignition that switches between direct ICM spark to ECM controlled spark advance.

So yeah I'd look at that as the problem. The easy thing to swap would be the ICM. The problem could be wiring or ECM also but for sure I'd try swapping the ICM and seeing if that fixes it. Wiggle the 4 wire connector on the ICM with the engine idling. No apparent damage to the engine wiring harness right? It would be worthwile to look at the ECM connectors to make sure they look good

Replaced ICM, so far, so good! I will keep you updated

Just had similar issue.. I had code 42, and I replaced my ignition coil... I did buy the ICM, but have not needed it car is running good so far. Are you still getting code 42 after changing ICM and resetting?

quote Originally posted by tbone42: Just had similar issue.. I had code 42, and I replaced my ignition coil... I did buy the ICM, but have not needed it car is running good so far. Are you still getting code 42 after changing ICM and resetting?

Working great now, no code 42, however.... Of course, it develops ANOTHER issue. during my test driving, the engine worked wonders.

I got onto the highway, and noticed smoke, oh boy, I thought, engine fire. So I pulled over and checked it out... no fire... but lots of transmission fluid. My speedometer Sensor Housing is blown, so the faster I go, the more fluid I lose. I also had my trans start to overheat, so it started slipping.

now I know I need a speedo sensor housing, finding one is going to be oh so fun, but why would I be overheating in the trans? the coolant is fine... could my TV Cable be not adjusted right, causing higher torque converter load, which results in higher temps? or maybe my trans cooler lines are backwards? :P