Hey everyone, I just had a question about engin idleing. I've only had the Bonneville for about 3 1/2 weeks now, but I've started to notice something that I feel is a little odd. When the engin is idleing, especially when the A/C is off, it will sometimes experience a sudden shake that can be felt throughout the car. Its abrupt and goes away quickly, but its is a little concerning. But I also notice that this car runs better w/ the AC on then when its off, which it totally opposite of my other cars. Should I get a tune up? Could it be a belt or something? Thanks for any help you can give.

The experts can better advise you... but when I had such a thing, it was a cracked/bad plug.

I would try taking out your idle air valve and inspecting it. When i would come to a stop light after driving for awhile, the car would idle at 650 rpm, but then after 20-30 seconds, the rpms would go slightly up.. then slightly down.. then level out at 650 rpm again.

there was a dark black sooty deposit on the valve that i cleaned off with some solvent -- careful to not get any on anything else other than the acorn shaped valve piece. now its a nice somewhat shiny aluminum color.

that seems to have helped me.. for now.

If you don't know when a tune up was done, plugs and wires is always a good starting point. On your specific problem, I agree that the IAC would be the first suspect. That is was does most of the work in controlling idle speed. Instead of just cleaning the IAC, I'd suggest a good throttle body cleaning.

Being supercharged...you don't want to hurt the coating on the supercharger rotors by spraying TB cleaner of ANY sort directly in while the TB is on the car.

The best cleaning method is to remove the throttle body (about $5 for the gasket). About a 1/2-full hour project ..very easy.

Thanks guys, I'm pretty sure it needs a tune-up at this point. I'll have to add that to my "To Do List." Hopefully that and a good cleaning will solve it. I was just worried it might be damage done by prolonged use of low-octane gasoline or something. I just have to find the time to get in there and get to work!

Inquiring minds need to know!

Well, I haven't had the opportunity yet to look into the idel problem and unfortunately, I think its getting worse. When ideling in PARK with the AC off the shaking gets violant. I'm taking it to a local Pontiac/GMC dealer on Friday. Im gonna see what they have to say about it before I do anything else. This way I also get to see how reputable they are. I'll update this post on Friday night to let you all know.

Well, turns out that the main problem with the Idel was the EGR Valve. It was apparently in very bad condition and needed to be replaced, which wasn't really a surprise, but it did run me about $150.00. However, the idel is MUCH MUCH better. I was told a tune-up is gonna be necessary soon due to degrading plugs and wires, but after 101,000 miles thats not a shocker either.