Hey All,
I'm helping a friend out with her Z28, it's got about 160k miles on it and the issue she is having is after the car warms up, it runs like it's missing. When the car is cold, it starts and runs like a champ, give it a few minutes and it starts running rough. Here is a list of things that have been done to try to resolve the issue.

• New Plugs/wires (properly gaped)
• Fuel injectors have been thoroughly cleaned inside and out
• Fuel rail cleaned
• New O-Rings on all injectors
• Fuel filter has been replaced
• Optispark has been replaced
• Intake Manifold/Throttle body have been thoroughly cleaned and given new gaskets
• EGR valve is new
• PCV valve is new
• ICM and coil test good
• Vacuum lines have been replaced
• Fuel pressure is reading 46psi at Prime and 40psi running

After doing all this, I'm really thinking it could be the O2 sensors or just a bad optispark. Even though the opti is new, doesn't mean it can't be defective. But the O2s haven't been changed at all.

I am pretty knowledgable on the LT1, I do work on several of them for my Impala Club. But this one is just throwing me a curve ball. Any insight would be appreciated.

-ImpalaMan

 

may very well be the 02s, its a good idea to change them every once in a while anyways. i think of changing them when im changing the trans fluid. it sounds like its doin it in closed loop so its a sensor and it sounds like youve changed everything but the 02s. is it throwing any trouble codes?

 

That's the funny thing, its not throwing any codes at all. But yeah, I didn't think about it maybe running in closed loop. I've got a Snap-On scanner so I'll plug that into it later and see what it says as far as open/closed loop. Thanks for the reply

-ImpalaMan

 

I wouldn't say its a for sure optispark issue till you can get a code readout.

 

Ok, checked the cars computer, the ONLY code readout I got was for an EGR issue, but the EGR valve and solenoid are new. The car is also running in open loop. So no issues there. BUT, the car only runs rough at idle, once you give it some gas, it smooths out and runs fine. I have NOT checked the O2 sensors yet, I am waiting for a buddy, who also has a 95 Camaro, to be available to swap out the O2 sensors from his car to my friends to see if that solves the problem. If it doesn't, I'll be swamped on this one. The only other thing it could be is the computer. Am I wrong?

-ImpalaMan

 

test the evap system and the gas cap.