Thread: 02 Grand Prix Rough Idle

My GP just started idling/missing badly this morning. I have had a catalyst code for the last couple months. The SES light just went off last night and now idling rough. Not sure if it is catalyst related or not. Here are some videos of it. When I rev it up, it runs smooth as normal. Thoughts?

https://www.youtube.com/watch?v=ZcEj...bn_fx7ESlYZhTg

https://www.youtube.com/watch?v=HEOz...bn_fx7ESlYZhTg

your vids are private, whats the code you have?

Fix the known issues..

Sorry..but its often very tough to tell you what changed on your car when it has a known issue that might plug the exhaust.

Originally Posted by Scottydoggs

your vids are private, whats the code you have?

Sorry, try now. Code is P0420.

dont fix it, it sounds like its got a huge cam lol kidding, but it sounds mean.

does it feel gutless when you get on it, the cel flash? if so your cat is clogged up. 420 code is a cat code too.

Originally Posted by Scottydoggs

dont fix it, it sounds like its got a huge cam lol kidding, but it sounds mean.

does it feel gutless when you get on it, the cel flash? if so your cat is clogged up. 420 code is a cat code too.

No, when I get on it, it goes like a banshee! even idling, if I hold the pedal at anything above 1,000 RPM, it is smooth.

maybe it just needs a tune up real bad? last time it was tuned up? plug wires are all in the clear? not melted. no vac leaks? spray the lines down with carb cleaner, if the idle jumps up you found the leak area. that evap Y line you n/a guys have likes to crack.

http://www.obd-codes.com/p0420 description of your code.

Originally Posted by Scottydoggs

maybe it just needs a tune up real bad? last time it was tuned up? plug wires are all in the clear? not melted. no vac leaks? spray the lines down with carb cleaner, if the idle jumps up you found the leak area. that evap Y line you n/a guys have likes to crack.

http://www.obd-codes.com/p0420 description of your code.

Thanks, I'll do some more checking on some of your suggestions tonight. Going to be cold as hell here tonight though!! Stuff needs to break on warm days!

Did new AC/Delco's and wires when I did Lower Intake gasket in 2010. Just seems strange it was running perfect this morning, shut it off, started back up 30 minutes later and it is acting up.

Sounds like something is heat soaking. Look around at the wiring like where it crosses from radiator to engine etc.

when the idle jumps like that and sounds like its got a nice cam, its 99% of the time a vac leak.

you have anyway to check your fuel trims? torque app or something? that will tell you if you have a vac leak too.

Originally Posted by Scottydoggs

when the idle jumps like that and sounds like its got a nice cam, its 99% of the time a vac leak.

you have anyway to check your fuel trims? torque app or something? that will tell you if you have a vac leak too.

My Scanner does some monitoring, but don't think it does fuel trims.

Well, if anyone wants that mean sounding lope in their idle, remove the large vacuum hose off the throttle body that comes from the evap solenoid.

Scottydoggs ... you hit the nail on the head! Thanks!

same line that broke on my car, sounded pretty cool. lol

fixed mine like this. fat vac line that fit the nipple, then a smaller line pushed inside the fat line, then to the hard line to the evap.

Mine wasn't even broken, was just pulled off the nipple somehow.

thats called old and dried out. only way it would come off. if it pops off again replace it. i replaced 80 % of my vac lines for 5 bucks, with new T's.