Sometimes my 02's stop cycling for a few minutes, then start cycling again, and I'm trying to figure out a miss I have only after tha car has been driven for a minute or 2, when its dead cold its fine. Would having bad 02's cause them to stop cycling, or is there somewhere else I should be looking? And when it misses, it just falls flat on its face, it jerks you forward its so bad. And when they don't cycle, they hang at 917-921...

 

Sounds like its temporarily dropping out of closed loop. Have you checked the coolant temp sensor? If it was providing an artificially cold temp to the PCM, it would drop out of closed loop, and possibly go into cold start enrichment.

 

You also go into open loop when at WOT where the mixture is not expected to be 14.7 to 1.
Does this only happen when you are "on" the throttle?

Tom Piper

 

Coolant temp sensor reads fine, its usually between 173-180 with my becool radiator. I've had one go bad before, and I know what thats like, its not the coolant temp sensor. I've checked all the sensors the scanmaster shows, and they all read fine. It misses when the 02's are cycling or not cycling, it really doesn't matter.

 

I'm talking about part throttle, idle, and cruising. I know they stop scanning at WOT.

 

Sounds like the same problem my buddy had. But his didn't miss fire when it did it.. It was from his PCM for less tune.. I called them up and they said it was something to do with CAT-overtemp ( since they weren't there anymore ) .. I sent the PCM back to them, he retuned it and problem was solved..

 

I know you said all the sensors look OK on your scans, but could the TPS have some bad spots on it, making the PCM think the throttle is open far enough to go into PE mode?

 

I'll keep an eye on it and see if it fluctuates at all next time I drive my car.