I have a 1991 stealth dohc that started to misfire lately. Wires and plugs are new. It misfires on three to four cylinders sporadicly. Checked out the coils, power transistors and numerous other things. Can the computer be causing this? Please help John

 

All the filters in good shape (air and fuel)? You may want to check out the "Idle Air Controller" instructions here--> Stealth316 IAC page
It could be the ECU, but without knowing for sure, that is an expensive "guess." Could be dirty or malfunctioning injectors.

Does the car do it all the time?? Only when cold? At first startup? Let me know, I'll see if I can help.

 

Thanks for replying,the things you mentioned are good, the injectors all test within the ohm range. It does't matter what temp. the engine is the problem is consistent. The stepper motor tests bad on one terminal. But would that cause the problem? Took the computer cover off and found no leakage around the copacitors but found some black residue on the board away from them. Does't seem to be burnt marks. John

 

Normally when the Caps on the ECU start crapping, they emit a very foul odor, like that of a beached fish. Very noticeable.

I would say that if one terminal is bad, the stepper is not working as it should and could be causing the miss. You might be able to pick one up used (there about 350+-new).

PVC valve working properly?? Does the CEL come on at all?? If it does, you can check the codes with an analog voltmeter.

Sorry man, I am drawing a blank right now.

You might want to check out 3si.org. There are some pretty sharp guys over there that may be able to help.

 

Ok, that's where I will start, hope to find a used or rebuilt one. Thanks John

 

I took the cover off the computer and found 1 capacator that leaked across part of the board. Took it to a local tv repair and they replaced the caps. Put it all back together and the engine still misses. Looks like I'm starting to throw parts at the car.

 

you need to replace your stepper motor and the capacitors in the ecu that are fried.. go to www.3sxperformance.com for all your parts.. they are verry knowledgable and friendly .. they only deal with the 3s platform....