Stumbles, surges and erratic idle
 

I have a 93 Auto and have had stalling and hesitation problems for some time now. The problems seemed to clear up after changing both the fuel filter and fuel pump sock. Now it's back and worse.

Here is the problem. At idle, the RPM's now vary from 750 to about 1100, with the AC off. When in gear the RPMs will approach 1000. I get occasional stalls when stopped for a light. When driving I get either a hesitation during normal acceleration or an outright stall. The car runs great at 70 mph (1800 RPMs) but if I get in it to accerate I will get a momentary hesitation (not a downshift). I have stumbling upon acceleration.

I have replaced the plugs and wires, the MAP,the filters, the IAC and the fuel pump (IAC and FP by the dealed). The dealer reports the TPS and O2 sensors as good. I have no codes set in the computer and have tried a new PCM and saw no change. The dealer said that the everything looks great but that the computer is losing its learned program now and then.


Any suggestions? I am at a loss and don't know where to go (unless to another dealer).

Re: Stumbles, surges and erratic idle (MEBVette)
 

Sounds like new ECM time, IMHO :seeya

Re: Stumbles, surges and erratic idle (carter200)
 

Been tried. Dealer put and new PCM in and ran car for an hour. Had the same problems. I am starting to think there is a bad ground clearing the computer but have no idea where to look.

Re: Stumbles, surges and erratic idle (MEBVette)
 

Did ya check the thin red wire going from the positive battery post to the ECM? I know my '86 has one... it's used to power the ECM, maybe yours is loose or broken?