GMC vortec OBD1 probs

4.3l vortec.. getting a little harder to start.. but runs great in open loop mode on startup.. after a few minutes idles like shit but wont stall and i can hear the motor backfire if i get on the gas lightly.. if i hold the throttle WFO the truck downshifts and accelerates like hell.. sometimes at mid throttle in this condition.. the van bucks and surges, backfires and gets going, then hesitates, surges agian...

the only code i get sometimes is too rich... i can force the code by putting the van in cruise control at around 40mph before the van starts to act up.

when the engine light comes on, the van (seems to) operates normally.. but must be in an open loop mode.. right?

this truck passed emissions about 6 months ago..

any ideas.. thanks

Reply to
zoomie
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Reply to
Shep

Wholly Full Open? Wide Fu**ing Open?

That's often an indication that a major input sensor is bad -- MAP, TPS, CTS, etc... If this observation holds true in every instance, then I would check sensor input readings on a scan tool first to quickly rule that possibility out.

Otherwise, you could be experiencing overfueling due to a stuck open injector poppet (there's one for each cylinder) as the code 45 would indicate, or as Shep suggested, a flaky regulator.

If the regulator or any of the plastic spider lines were to leak under the manifold, or if a/several poppet(s) were sticking closed (common problems) the truck could run like crap but I can't see why you would get a rich code without another unrelated problem. Of course it is early in the morning and my thought processes have yet to receive a needed kickstart.....

Toyota MDT in MO

Reply to
Comboverfish

I've had to replace the ignition control module on my car twice. It caused fast idle, bucking, and random stalling. They can be removed from inside the distributor and taken to some parts stores where they will test for free so it's a pretty easy one to eliminate. Mine had a 5 year 50k km replacement warranty. If replacing I'd recommend bedding in a bit of thermal dielectic grease from an electronics store, the stuff they bed computer CPU's in. One packet costs $1 here. I think dry bedding by a mechanic caused my first replacement to burn out.

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