Off idle stumble...................

[Paul Workman]

Originally Posted by tomtom72

Jeff,

I'm with Brad on the injector issues. However, I'm thinking that "off idle" is the only "stumble"? If yes, then I think that eliminates alot of things like, plugs, wires, coils, f/filter, fuel pumps (maybe) and injectors (maybe). What I mean is no other miss going up thru the rpms, after the initial off idle miss kind of rules out most all the stuff I mentioned.

.... then open or closed loop operation? because that may tell ya something....different sensors in both phases of operation come into play. Know what I mean?

Open loop = cold start, then is TPS set right? Is IAC doing the right thing? Are temp sensors doing the right thing? Are the plugs too cold? PCV's okay? Is there a small vac leak or does she idle @ the right #?

Closed loop off idle stumble, my 1 suspect is the TPS, then O2 sensors, then the recalls/TSB's on any EPROM issues ( unless this issue is "new" to your car? ). Again a small vac leak or clogged PCV's. Plugs too cold? Heat related failures of the injector coil & wires & coils & plugs usually result in a solid miss everywhere...ya know it just don't run well....you didn't mention that so I knid of rule most of the ing & fuel system out.

Oh, I'm with Brad on the scan as it may show what's up with the electronics.

JMHO

Tom

Dittos on the scan. With as many things that will produce symptoms that are the same or similar, the scan will really narrow down what is and isn't working in very short order - giving you a starting place. The Z is my second Vette, and as it happens it was my second opportunity to have to troubleshoot a (stumbling) problem. In my case, it wasn't what the scanner said was wrong, but what it eliminated that eventually pointed me in the right direction. Scanners (or a laptop)...I feel they are essential as far as keep one's sanity when problems pop up. W/o it, I would be religated to "shotgunning" the problems, and me hates dat!!

P.

PS. BTW, the scanner didn't indicate any particular fault. The injectors ohm'ed out OKay, and a leak-down test showed they weren't leaking. Making a LSS, mice had ruined a couple wires resulting in off-idle stumbling and stumbling at other intermittent times (depending on whether the wires were wet from condesation or not!).

Good luck!

P.