Rough idle and vibrating
 

hello, i have a rough idle on my 99 v6. It only happens when slowing down to stop, when im stopped, or in park. The whole car shakes/vibrates when stopped also. On a cold startup the car starts fine but if i turn it off then start it awhile later it takes a few seconds to start The battery and alternator are fine. When i slow down to stop it sometimes makes a small vibration in the front of the car. We took it to a shop and had the mechanic go through it. He scanned it but no codes came up and there is no check engine light on. He fixed a small rear leak on it. He found moisture in the gas tank so he took it off and flushed/cleaned it out. The moisture made it to the fuel injector filtor so he took off the heads and did a full cleaning there to. He also fixed the transmission mounts. After all that it does alot better but still has the symtoms i mentioned above. Any suggestions?

did you clean your throttle body and IAC?
sometimes there's too much gunk in there that it doesn't smooth out your idle.


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I'll try that and see what happens thanks!

Well last night I was driving on the interstate and noticed the check engine lick came on. I turned the car on this morning and it came right back on so now I guess I can take it to get it scanned.

is it flickering or steady? if it's flickering then it's misfiring.
post the codes here. you can also go to auto parts store and have them scan it for free.

my "service engine soon" aka "check engine" light doesn't work anymore so you're lucky..



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The check engine light is steady we scanned it and the po455 code came up saying evap system leak detected. Would that cause the rough idle?

check your gas cap, tighten it or replace with new one. reset the code (by disconnecting battery or the scanner) and see if the code come back. Have you checked for "pending codes" ?



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the gas cap is already new and is on tight. we had the car scanned at a local place my dad goes to and that was the code that the guy showed us on the scanner. we are taking it to the shop that we already had it serviced last week. they said they would look over the car again to find whats causing the code and hopefully find whats making it idle rough. Hopefully they can find it the second time around.

you might have some vacuum lines that are leaking, especially on the purge valve. needs thorough checking on your fuel lines too.



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Thanks for the suggestions; will let you know how it turns out.