I have restored a 1990 IROC-Z (5.0 TPI 5 speed) to original condition, but it's performance always seems to be lacking compared to a similar IROC-Z I own.

Sometimes when you accelerate at about 2/3 throttle, the engine will noticeably derate power once it gets to about 2,700 RPM.

It sometimes logs code 32, but the diagnoistics for this code do not reveal any problems.

Sometimes the car will gradually lose power and it will act as though the fuel is being very slowly reduced to zero. I have done quite a lot of testing and found that as this is happening the fuel pressure remains within spec all the time. But here is a big clue; if you turn off the ignition (manual trans) for a few seconds, and then turn it back on. The problem disappears completely and may not happen again for the rest of the day.

One day recently, I was going to recheck the base ignition timing once again. and I noticed that the ignition timing does not change when the DST is disconnected/reconnected. I replaced the ignition module in the distributor and it made no difference at all.

Now my Snap-On scanner will not connect to the ECM.

As I understand it; the ignition module contols timing in a very basic rudimentary way if the ECM, etc. should fail. But normally the EPROM controls ignition timing. Do I understand this correctly?

Is it ""probable that the EPROM in the car has some issues, and the entire problem is that the ECM is not controlling the ignition timing, and the code 32 could be caused by ignition timing being chronically late (EGR temp out of range for engine load and operating conditions). Can the EPROM be tested? A new one from GM is $250.00.

I have become so discouraged by this that I have stopped driving this beautiful car (bought a 2002 B4C to drive).

I sure hope you guys can help me out with this problem.

Thanks, Andy,

 

Hey Andy,

Long time no see! I remember my drive in that beautiful car!!

I can't remember if your car is SD or MAF or even if that matters here, but while my ECM is sitting on my floorboard, I'd be willing swap my ECM into your car w/ your chip if you wanna do that just to rule out your ECM.

89 Formula/MAF/ECM # 1227165
Can I be of any help to you?

Eric

 

Thanks, but I don't think the '89 will work with a non-sd eprom.

 

I just picked up a 1987 transam 5.0 tpi and in the receipts there is a work order for a new computer, that states engine was missing and losing power a 2500 rpm and above. they replaced the computer and it runs fine now. Hope this helps.