The car runs and drives fine when cool no stutters or misses once warmed up the car misses and at cruising speeds kinda skips a beat now and again rather frequently i checked fuel pressure at idle and it is 38 psi and 46 with the vaccum line removed, i had the icm tested and it was fine also it is pretty new less than 500 miles. So does this sound like an opti problem or is it possible that the icm gets heat soaked and starts failing. Any help will be much appreciated.

 

Actually, it's sounds like an EGR issue to me. While the OPTI can have symptoms like you describe, it's more likely to have high rpm breakup issues.

Try making a block off plate from aluminum or steel using the gasket as a template. If that doesn't solve it, look to the opti...but only after you've examine the spark plug wires closely...

Good luck

 

already have egr blockoff plates installed could it be that they are leaking there is high rpm breakup in fact it sputters and misses at all rpms

 

It sounds like it may be O2 sensors, although usually if they are that messed up they'll throw a code, but not always. If it does it at WOT too though then it's not them since the computer ignores them at WOT.

 

sorry i already ruled the 02s out as it gets worse as it gets hotter for instance sitting in traffic when it reaches 220 the car feels one cylinder down when cruising engine temp at 160 it just skips a beat here and there rather frequently definately not a closed loop deal and it does it at wot too.

 

also as far as i know the opti is a stock unit with 154xxx miles on it so thats pretty good for all thos opti haters out there if that is even the problem any body agree with my diagnosis?

 

Have you scanned for any codes? There is an icm spacing mod on shoebox's site that may be helpful if the heatsink is getting too hot and failing. Im kind of having the same problem right now on my car and i have dtc16 which is the opti sending weak spark at low rpm so hopefully yours is just the icm. get that sucker scanned! good luck!

 

good point i haven't had it scanned yet i already did the icm spacing mod i was thinking it could be either the icm or opti im going to have it scanned tomorow any body with any more ideas would be greatly appreciated.

 

I don't understand. You said you had it tested and is good. It's new and yet you still think it could be the problem. Either your brain can't wrap itself around the fact that it could be something else or it won't move on until it is replaced. In either case it's time to go to something else.

3 major points here. If you think something breaks down when it's hot why not break out the hair dryer and warm it up on a cold morning to see what happens?

2nd. When was the last time it had a tune up????? Coils are considered tune up items. They break down quite frequently. A look at the coil while running in the dark can be useful. So is a visual inspection of the casing looking for tell tale white spots is an indication of misfiring. Then there is the fact that even an opti has a cap and rotor which need replacing from time to time.

Last. Is it entirely possible you have a closed loop issue? You said the O2s are good and don't seem to have any hesitation regarding that. How do you know if you don't have a scanner?

Have you tried to unhook one of the O2's? This is the easiest thing to do to see if you have a purely "closed loop" issue. If you did, then once the engine gets up to operating temp. with the O2 unhooked it should run ok.

 

The o2s are not the problem as the stuttering and missing becomes worse and worse as the engine gets hotter and hotter. The last tune up was about a month ago. The coil is brand new. Also the only code I am throwing is a code 32 egr system fault, my egr is removed and this code is stored from when i drove the car with no resistors in place of the egr solenoid and the solenoid detached. I have heard of an ICM testing good over and over and once heated up still failing. I don't have "cold mornings" where I'm at and im pretty sure a blow dryer won't get it hot enough becaues the problem doesn't start until operating tempurature. I have proper fuel pressure and injectors were just cleaned when i did the cam install about 2 months ago. So I have narrowed it down to 2 things either the ICM gets heat soaked and begins to fail or, the more likely culprit, the optispark, after years of service, has finally went south. Any more problems with my logic?

 

Is this a new problem or has it been happening since the cam install 2 months ago?

I think that may point us in the right area. If it ran great after the cam install then started acting up, then it sounds like an electrical issue. Possibly the opti or even the O2 sensors. But if it has been crap since the cam....then it could be an issue with the install and centered around what was replaced and or put back incorrectly.

More info and details might help narrow it down further.

 

New problem about a week ago in fact i don't think it has anything to do with the cam but hey who knows i guess it just seems to be all signs pointing towards ignition

 

Mine does the same thing has ever since I bought it the begining of the year and the OPTI is the only thing I havent tried. But with LTCC the only thing in the OPTI I,m using is the OPTICAL sensor. So I cant see spending the $300 bucks just for that.

 

believe or not, oil seeps up the shaft and oil get on the opti sensor. a dab of silicone stops the oil from seeping in. the opti drive shaft is two pieces. when you take a high mileage opti a part, you will a brown film inside. I believe this to be oil.

With 154,000, it is time for a new opti from GM!

 

I was actually wondering if it didn't get some oil in the opti from a seal and then start to make the opti fail i will have to see what it looks like when i have the cance to remove the opti.