Every once in a while, my engine wants to idle higher than usual. Normally, it's 650 in park and 550 in gear. When it's acting up, it'll be 850 in park and 700 in gear. When this happens, the transmission doesn't want to shift when it's supposed to. No matter the throttle position, the tranny always wants to shift a few hundred rpm higher than it's supposed to. The best way I can describe it is that it will rise a few more hundred rpm and then hold the gear (plateau) a few seconds and then shift. It will do this for about a day or two then be fine again for a while. Is this some sort of vacuum leak in my engine? Has this happened to anyone before? I'm not sure if one issue is causing the other. This issue KILLS my gas mileage. Thanks for the help!

 

Usually a vacuum leak will throw codes, like P0171 and P0174 for both banks running lean. I'd check for any codes, even if the SES isn't on.

 

The only code is a P0430 (Catalyst deficiency - Bank 2) Would THAT cause it?

 

P0430 is the passenger cat inefficiency code - could be clogged or coming apart inside. Are you aware GM extended the cat warranty on the 00-02 F cars to 10 years/120K?

Edit: www.gearchatter.com/viewtopic9138.php

 

They've already been replaced at 72k, now there's 157k on the car. I don't see that causing the issue I sometimes have. Is that something I should just live with if/when it gets worse?

 

It could. The material inside sometimes breaks up and can turn sideways and plug the exhaust and that can cause all kinds of problems.

 

I see. That makes sense. Well, I guess I'm just gonna have to get those Pacesetter LTs after all....damn, I hate it... While I'm on the subject, any suggestions on a decent, affordable exhaust? If I'm gettin' rid of the cats, I'm gonna do a full exhaust.

 

The True-Dual setup from TSP sounds about as good as anything you'll ever hear on an F-body.