Happy new year! Unfortunately I think mine comes with a problem - my DD C5 is going nuts after the first cold-start of the day in temps below ~50deg. The colder it is, the worse it is.

Upon ignition the car starts fine - but once it settles and begins to idle everything goes downhill. It will settle @ 800rpm for a small bit and then start to fluctuate greatly between 400rpm and barely staying up, back up to 800rpm and then will randomly rev up to 2000rpm+ even though I'm not touching the gas pedal at all. While idling it feels exactly like it would if it had a big cam - but it's just a bone-stock z06 w/ an exhaust. This might be due to it sometimes throwing out a P0300 missfire code - but it's only temporary.

Once I start to drive it - it will sometimes act like the throttle i stuck and stay at ~1500rpm in neutral, when shifting gears it feels like the flywheel just never stops and the engine will not drop in RPM's at all until i'm in the next gear. The car will literally accelerate itself without me touching the gas pedal in 1st or 2nd if it's cold enough. Also, when moving from a stop, sometimes the throttle response goes to basically 0 and the car barely stays on until it all of a sudden goes nuts and revs to 2k+ rpm again. Completely ridiculous.

And then it all goes away once it gets warmed up (when oil temps hit ~100deg+) and drives perfectly normal. I'm dropping it off at the shop once I go out of town this week, but I was curious if anyone else has had this issue and figured out what was causing it? Thanks for any help!

 

Any codes? I had an issue with primary oxygen sensors that caused a similar fault.

 

Did you do the throttle body bypass? My trans am did this when I did the throttle body bypass.

I had to put it back in during the cold times.

 

I've seen the P0300 code pop up twice, but it goes away quickly. Oddly enough I just got codes P0171 and P0174 this morning. Lean codes.

 

No sir - at least not to my knowledge. I bought the car used last year.

 

I agree. My 03Z likes to have the connection just after the MAF slip off. When it happens, the car runs distinctly different.

 

Honestly, I'm a complete newb when it comes to knowing what to look for under the hood - the "air plumbing" between the MAF and TB is just that giant tube coming from the intake, right? If so, I checked that and both ends are sealed fine. before and after a start-up.

What PCV hoses could I check? I don't know what hoses are part of it besides one that I had to unplug while changing out the SWPS. That one was fine. Also just found out I have a very slow oil leak looking at my parking spot. Might be another problem caused by whatever is going on lol

 

is the coolant temp gauge working properly?

 

Yes it does. Gauge matches the temp readings on the DIC.

 

Any modifications?

I had a FAST 90 where the upper warped and it did not seal between the TB and intake. It would climb RPM in gear, and idle high.


Check your vacuum ports on the intake, MAP sensor grommet, line to the brake booster etc. If you can find a smoke machine, it maybe very helpful.

 

None that I can see - It was bone-stock when I bought it and all I have done is put aftermarket axle-backs. I will check those out tonight.

The brake booster line is fine, that's the one I had to mess with while changing the SWPS.

 

are those readings correct is what I was getting at... a faulty coolant temp sensor can cause the car to run horrible