Can opti-spark problems be intermitent? I am having a stalling issue that I can't seem to figure out. My son has been running diagnostics on it but cannot pinpoint the problem. I get codes 36 & 42 after it stalls. It just quits in the middle of the road. No sputtering or backfiring. It runs perfect until it stalls. I have changed the coil and the ICM. It is a 94 Auto with 72k on the clock. Any help would be greatly appreciated

 

I just had a code 36 on my 93. A check engine light came on after a few starts,it never stalled though.I did not drive it after the check engine light.Check your water pump for leaks above the opti.There is a weep hole on the back of the water pump that will drip down on he opti when the pump goes.The code 36 is the opti(the high side) If you have a fsm (manual) you can use the diagnosis in the book. Mine was the opti.I would pull the ICM and get it checked just to be sure good luck Tim

 

I would have to say that anything is possible. But I would sure look at all the other possibilities first. I would shake and pull any ignition wiring I could get my hand on. Including connections at the PCM and opti. Look for any pushed pins in the connectors or corroded ones.

I know you are getting the codes, but I would just like to get a look at the fuel pressure just to make sure the fuel pump is not cutting out.

I would sure would test, check and look at all I could (and use up all the beer) before I changed the opti. If nothing turns up, then go to opti land.

How often does it die, and does it start right back up?

 

It dies everytime. It will idle forever (I think) but dies as soon as I go down the road. It will start right back up and then die again. I have changed the coil, ICM and the Opti harness.

 

The beer is almost gone now. I have been trying to figure this out for a month now.

 

Have you checked the fuel pressure? Sounds like its dying under load?

 

Might be elementary but how about the fuel filter.

I would at least hang a FP gauge on it and go down the road just to make certain which area you are in, fuel or spark.

 

Good information and definitely worth a check.

 

I have not checked the fuel pressure but it might be a good idea. Would that throw codes 36 & 42?

 

Obviously a fuel related problem would not throw the codes. But you already replaced the coil and ICM. The opti is a much bigger and more expensive job and before you go in that direction you at least want to make sure it's not a simple fuel starvation related problem.

 

Red-LT1,

My car does EXACTLY the same thing and is the same year. The only difference is my car is a manual, not an automatic, but I don't see what that should matter. You and I are going down the same road, but I have gone a little farther. I have replaced the opti-spark, ICM, PCM, opti-spark harness, fuel pump, AND fuel filter.

Note that I did not take a throw parts at it approach and see what happens, but still, here I am. Maybe I can save you some money in parts and we can figure this out together.

I replaced the fuel pump and filter just out of maintenance thinking that might be the problem, but when it didn't solve it, I started to really do some diagnosis. I bought the service manual and ran all the tests it called for. I even hooked up a data aquisition board from National Instruments and monitored these signals: high resolution signal from opti-spark measured at the PCM), low resolution signal from opti-spark (measured at the PCM), signal from PCM to ICM (measured at the ICM connector). Here is the video of those signals (http://www.screencast.com/users/russ...d-d49c91d430cf).

Let me know how much you know about the functionality and I can fill you in on what I've learned. There is a low res pulse from the distributor (8 pulses per cam revolution) and a high res pulse (180 pulses per cam revolution). The engine can fun on the low res pulse alone, but refines the timing with the high res pulse. Code 36 results when the low res pulse is present but the high res pulse is not.

You can see the low resolution signal on the bottom, high resolution signal in the middle, and signal to the ICM on top. I rev the engine and the frequency of these changes.

What is not on the video is what happens when the engine fails. Both the high res and low res lines go to 5V. I assume the distributor "biases" these lines when it is working correctly and pulls them low.

According to what I have read, code 36 results when the low res pulse is present but the high res pulse is not. When I replaced my opti the behavior changed. Before I replaced the opti, it would die at random just like yours and otherwise run perfectly, but there were no codes. After I replaced the opti, it took some time cranking (5-10 seconds) before it would start, but after starting it ran well except for certain situations. When on the freeway in 6th gear and floored, it feels like it misses every now and then. I also have code 36 stored now. My guess is that the high res pulse is no longer there and the timing is not as precise as what it needs to be resulting in a miss every now and then.

I plan to hook up the DAQ board again and scope these signals to see if the high res pulse really is gone. I think there is still a fundamental problem that I'm not finding. Let me know what you come up with and if you have any questions. I will keep you posted on my lack of progress. This has been going on for me now for five months.

 

Yes opti symptoms can and will be intermittent. I've had 2 optis die and both gave my fair warning of their pending deaths.

 

WOW, that is a lot to digest. If I understand correctly, the stalling did stop when you replaced the Opti? I have been trying not to throw parts at it either. I can change parts no problem but when it comes to the diagnostics and the electronics - I suck. My son has been doing that. I have the FSM and he went through the flow charts. At first he thought that it was the PCM but now is not sure. What brand Opti did you buy? Have you changed the spark plugs and wires?

Please keep me posted with any progress that you make and I will do the same for you.

 

according to GM manual book the 36 code with 42 code showd at once ,says the pcm or pcm harness .
so before trying to change the pcm check the harness attached to pcm first ,if nothing changed then chang the pcm.
i'll try to give you more details.
good luck

 

here's some details:
if a dtc 41and/or 42 is also set with a36 dtc,and no external fault can be found then replace pcm,if only 36 dtc is set and the opti connections are ok then replace opti distribitor.
the external fault menssioned the GM book is the harness shortcut or connections for pcm or opti distribitior or coil and coil module.
this note taken from GM service manual book -book2 section 6e3-a-82.
good luck

 

That is interesting. I am getting DTC 36 & 42 at the same time. It's looking more and more like the PCM. The PCM is much cheaper than the opti.

Thanks for the info.

 

you welcome

 

sorry for jumping in here but I have to ask on my 93 ruby I have a no start condition fuel pressure is good and I am showing codes H41 & H54 any help would be apriciated

 

You cannot look at all parts as having the same probability of failure. The ICM although connected to the coil and could have similar codes but the ICM fails much more than a coil. And also if you have read any amount of posts, the opti fails frequently as compared to the PCM. The PCM actually has a rather low failure rate and hardly ever hear of one actually being bad and correcting a problem. PCMs are actually very reliable unlike the ECMs in the earlier years. The opti fails left and right all the time.

I hope you have done some of the basics as suggested. The PMCs might be cheaper but harder to find. It bothered me you can't it to crap out in the driveway where you can take measurements. If you go for the PCM, I would hang on to my original one.

 

I had the same problem with my 94 and the dlr said $400.00 and we can't fine the problem!
Well I bought the ignition switch and when it died I did what the look smith told me to do and it started,seemed just like the passenger reached over and turned off the key.I then checked the coil and no spark to the coil and no injector pulse.Replaced coil and car fired and ran for a few mths.It died again and I got pissed and shipped the car to my son.The car ran a mth and died.He took it to a chevy dlr (diamond chevy) near palmsprings.
They replaced the opti and the water pump.Car runs fine just like before,but now it over heats runs around 240 to 250 now and they want to replace the ecm because the fans come on to soon.
Now they found out they can't get the ecm so now it is a stale mate.
They say the water pump is good . The car was not over heating before it went in for the opti .Moral is the chevy dlr says we don't believe you! that it was not overheating and they just say the fans are coming on to soon, that is why the car is overheating,I do remember my mom taught me when the soup is hot to blow on it to cool it down .I guess she was wrong in what she taught me when I was younger.They did get rid of the stalling problem