The engine runs good, very good; except at ramdon times, when HOT, the engine will buck a few times...then go back to normal, may be buck a few minutes later, may be not. This has only happened one time since last Saturday after replacing the OptiSpark unit and WP. The engine got a bit hot sitting in traffic this morning, but no bucking at all.

I checked for codes after that one time, but nothing set.

Have to see what happens I guess on the drive home this afternoon. Air temp will be around 100 and lots of stop-n-go traffic.

I checked the fuel pump output just in case....it has good pressure, holds pressure for several hours too.

It has got to be some electronic component that is getting HOT and causing this....I just do not know what it is.

OKAY; on the way home... lots of engine bucking, or cutting out...and then it finally died and would not start again.

Pulled the codes right then....Code 16: Low Resolution signal missing.
So has my new OptiSpark unit of 3 days gone bad? The engine started cutting out after only a few miles of driving last Sat and now it died. It did start back up after cooling down for about 45 minutes, long enough for me to get home.

NOW WHAT?????

 

ttt....new info.

 

Sounds like you are back at square 1 in regard to the original post and symptoms. If I have this right, you have replaced the opti, coil and ICM. As much as you would like it to be the opti which would have resolved your problems, it doesn’t seem to have changed anything by replacing it. It just does not seem like you replaced the problem part yet. All in all it doesn’t appear to have the symptoms of a bad connection or broken wire somewhere. It sure sounds like a heat related problem so I tend not to think about switches and relays.

You indicated in your original post the PCM was rebuilt. But what does that mean. Not like doing a engine or mechanical rebuild job. When generally testing or repairing electronics you are looking for failed parts but don’t generally replace parts that are working (unless suspect). If an intermittent problem existed with it, it might not have been discovered especially if it is heat related. If there is some sort of 5 volt regulation problem in the PCM, it could affect proper operation of the opti and dropout of the low resolution pulses. I’m just saying here in regard to all that information, it seems that the PCM could still be in the running as potential problem.

I wish I could pin point your problem or give some additional great suggestions, but finding this problem by shear testing is probably going to be tough since it quits on the road and you can’t carry you shop with you. I think you are on a good track by replacing some parts. I would never recommend to just throw parts at it but due to the nature of the symptoms, only time and driving will actual tell you when you are really fixed.

In the past I have wired LEDs into strategic parts of circuits to catch intermittent problems. This would take the place of a meter and gives immediate indications. Of course this requires higher level of electronics knowing how to wire it safety and what the indications mean as you configured them. This is just on one of my creative approaches but might give you some additional ideas.

 

First thing I would do ,if you haven't already, is check each plug in the circuit and clean them with electrical contact cleaner. Obviously you are losing the signal when hot when something is changing and probably opening a circuit(probably by expansion). How long did it run right after the opti change is it doing the exact same thing as before or is it a little different. And yes optis can be bad out of the box but you need to go over the whole ckt to rule that out first.

 

Here is what has been replaced: coil, OptiSpark, PCM "rebuilt" (whatever that means). I tried the igniton module from my '96, but have since found out that they have different part numbers, so maybe that was not a valid trial. Engine started and ran fine until hot and then the cutting out started again.

How long did it run without cutting-out after OptiSpark replaced was less than an hour. Made three short trips: 8 miles then stop for 15 minutes, 7 miles then stopped for about an hour, 0.5 miles stop for gas, then headed for home, got about 500 feet from gas station and it bucked...got home fine. Total run time of about 30 minutes.

Last night was the first time it completely died for me. When it began to cut-out, I could just press the accelerator pedal and sort of "power" through it, but only worked for a few miles until it died and would not restart.

I tried wiggling the wire harness coming out of the OptiSpark, but still would not start.

As far as the "rebuilt" PCM...yeah right....have no idea if anything was replaced, got no information back with it. And since this is a heat releated issue, they may not have been able to duplicate the failure and just sent it back to me even though I paid $200.

I am going to borrow a PCM and try it, just to rule that out. Wonder if I should throw a new ignition module at it? Trying to troubleshoot an intermittent heat related problem is just not easy.

 

You got 30min of runtime with no issues right? In that time it was at full temp correct? You had no code at that time? Now you have a code 16 and it won't run. Sounds like a bad opti to me sorry to say. Where did you get it from? Of course rule out every other option but optis fail in 15sec or 15yrs.You would not be the first person to have to put multiple optis on a car.

 

Yep car ran for 30 minutes with no problems...but it normally does this. It only fails after coolant temp stays above 210, which it does as air temp is around 100 and driving in traffic.

So my thought is to push a test wire into the OptiSpark harness and find the +5V supply and monitor this with the engine running and see if this drops out when the engine starts cutting out. If so, then it is the PCM which did not get fixed. Anyone have a wiring diargram of that 4 wire harness coming out of the OptiSpark?

 

Okay,
with a borrowed PCM sitting on the passenger floor and tools to change out the PCM I drove to and from work.

Yesterday coming home, engine begins to cut-out, tach needle bouncing, comes and goes.

I get the car in the driveway and let it idle; cutting-out, revving up, comes and goes. Within five minutes it has died and will not restart. I quickly put a fuel pressure gauge on, just to be sure. Engine does start and run....fuel pressue is 40psig, begins to cut-out and revs up once again.

Shut it off, swapped in the other PCM...start engine, running smooth, let it run for five minutes....no problems at all.

So I think I have determined that the "rebuilt" PCM still has a heat releated problem that is not fixed.

Auto Computer Exchange is the place that "rebuilt" it....so much for their work. Going to be sending it back to them AGAIN...may be they can "fix" it this time.

 

You Need to replace the whole opti-park. Not just the cap and rotor.
Take from someone who knows.