My 94 z28 started having stumblig problems yesterday. Basically, the car was in traffic a long time, then the engine starts to stumble/rough idle, and the check gages light goes on. The oil pressure reads low, just sitting over the redline, and it's running at 500 rpm. I should mention, it's been reading low for the 2 years I've had the car, so those marks seem normal. Suddenly, the engine revs to about 1000 rpm, then drops back down to 500. A day later, the car runs fine, but I need to figure this out. Just to throw these out there...I've searched posts suggesting it might be oil pressure sensor related, time for a tuneup (It's got 70k miles, stock plugs/wires), or something more serious. Any ideas?

 

The CHECK GAUGES light came on? Did you look at the temperature gauge?

 

no problem with the temp gauge...below 200

 

I wouldn't be comfortable with that low of oil pressure. I'd change the sending unit to be sure, if it was still low, I'd rebuild. Crank and cam bearings etc. I'd also do ALOT of upgrading to aftermarket parts.

 

Would a bad sending unit cause stumbling like that? And what about the engine revving to 1000 rpm? Thanks for the responses.

 

IAC man, it controls the idle speed. I'd check that out.

Brian

 

Okay, I think it's narrowed down to TPS or IAC. The low oil pressure could be a red herring, but in any case, I'd like to address that problem after this phantom revving is taken care of. Which one, TPS or IAC, matches the symptoms more?

 

Last year mine had those same issues.

It actually creeped me out when it would jump rpm's at idle, from 600 too ~1000 and back down.

I changed my optispark and that cured it.

But along with the opti, i changed wires and plugs, and then put a new transmission in the car.

So it could be a number of things, because for me it wasnt the IAC.