2004 Cavalier P0455 code - engine revving

[jbooth]

Dear all,
I have a 2004 Cavalier, with the 2.2-L Ecotec engine. Recently it has twice revved high while in neutral (it's got the 5-speed standard box).

The first time this happened, it went up to about 4,000 rpm -- with my foot OFF the accelerator. I turned it off for a minute and it restarted no problem, but I got the dreaded Check Engline light. I did an OBD II code check and got P0455 (Evaporative Emission Control System Leak Detected - gross leak )

Second time, engine revved up to about 2,500 -- again with my foot OFF the accelerator.

I'm going to look at the gas tank cap and the Idle Air Control Valve.

Anybody out there ever have a similar problem ... any ideas on what's going on?

Thanks in advance for your help
Jeff

[16th hippy]

gas cap would be first suspect for code, but could be other problem. if idle surge is connected to code, could be purge valve, or a vacuum leak around there. just for the sake of ruling it out, if equipped, turn off cruise control.

[jbooth]

OK, here's the update to my revving problem.

After reading posts on this site and several others out there I decided to pull out the Idle Air Control valve (IAC). This took about 15 minutes and could have been done much faster if I hadn't had to search for some of my tools.

The valve looked a bit carboned up. So, I let it soak in some intake cleaner and, after cleaning it off as best I could, replace it.

Everything seemed OK for about a day and then I revved again at idle, and the RPMS went up to about 2,500.

So, I decided to bite the bullet and buy a new IAC at the dealer. Cost about $175 CDN. Upon receiving the new part it was clear that the original had a problem, in that the new one had it's "plunger" out nearly a centimetre more.

I took the tools I knew I needed to do the "remove and replace" with me and did the part swap in the parking lot of the dealer. Total time here: 6 minutes. (Mind you, this time I know what I was doing and didn't have to hunt for any tools).

That was more than two weeks ago -- and the car has been just fine since then. No more high revving at idle.

The problem was, clearly, the Idle Control Valve.

The error code I mentioned in my original post appears to have been due to a gas tank cap been loose, theby allowing the "gross leak".

I hope this helps someone.....

Jeff