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i have an 04 colorado that is now out of warrenty and it has a rough idle... do you guys know what causes this? i dont really wanna take it to the dealership.
 

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Clean the throttlebody.
 

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Not really. But you might want to clean the MAF also.
 

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I posted directions for cleaning the TB about a year ago - unfortunately, the picture is no longer available, but here you go:

LINK

Edited: Better yet - check out these instructions:

LINK
 

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jokerjustin99 said:
i have an 04 colorado that is now out of warrenty and it has a rough idle... do you guys know what causes this? i dont really wanna take it to the dealership.
Hold on a sec here, please elaborate on your rough idle symptom. Is it just a little bad or is it noticeably misfiring? If you let it sit and idle for a good 45 mins does the service engine soon light come on? I would take it to the dealer asap and have them do the leakdown test to see if you qualify for a cylinder head replacement under the head replacement warranty extension. It should be free.
 

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My truck acts up and idles rough front time to time... it's not misfiring or throwing a CEL. It's the nature of the I-5... they all seem to do it. Every canyon/colorado I've driven acts up.

Mine seems to do it the worst when I'm leaving work sitting in traffic idling on very cold days.

I've cleaned the TB and it makes no difference in my case.
 

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Same thing here. I live in a nice weather zone and still have problems with a rough idle. I've cleaned the MAF and TB, and replaced the plugs with Iridium. It got a little better, but I can still feel it in the steering wheel. I'm not sure what to do next. My truck has never thrown the CEL in 80k.
 

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^ There really is nothing you can do... it's the nature of a I5 motor. It has an odd firing order and an odd number of pistons. It's not a naturally balanced motor like an I6 or V8.
 

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Cobra4B said:
^ There really is nothing you can do... it's the nature of a I5 motor. It has an odd firing order and an odd number of pistons. It's not a naturally balanced motor like an I6 or V8.
That may be somewhat true, but some trucks have a really rough idle. Mine did, and felt like a misfire, but never threw any codes, or CEL.
 

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^ Well I have my head issue coverage letter saved in my Canyon file if the issue ever gets to that point! I got the truck in March with 12,500 miles on it and am at 33,500 now... yeah I've been driving the crap out of it... been a wonderful truck.
 

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My worry is if it is the exhaust springs it may not rear its ugly head for another year.

At that point I'll most likely be over 100k and it'll cost me a fortune. :?
 

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^ Gotcha... I'm at 33,xxx. And it's not the springs... I believe it's a valve guide/seat wear issue to the point that the valve don't seal correctly. I think replacing the springs was an initial bandaid fix, and the current solution is a replacement cylinder head.
 

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my 3.7l runs real smooth. it has 11,300 miles on it now. i dont think all the i5 engines run rough, tho i dont know anyone with a 3.5l to compare it to.
 

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^ My engine itself is very smooth when driving... it just has some steering wheel vibration at idle.

On very very cold mornings it can be quite bad. One morning when it was around 20 I popped the hood and watched the motor shaking like the cam'd V8 in my Z06 does haha.

I have an extended warranty, and the GM letter for the valve guid wear issue so I'm not concerned. If it gets bad to the point hte truck is misfiring then in for warranty coverage it goes.
 
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