Rough idle

Asked by Oct 20, 2015 at 05:46 PM about the 2012 Chevrolet Colorado 1LT Crew Cab RWD

Question type: Maintenance & Repair

I just bought a used 2012 Chevy
Colorado the inline 4 cylinder LT. The
truck has a rough idle we scanned it
because the CEL has been on for
misfires in cylinder 2. I got it through
a dealer and we have them the truck
the said they switched coils from 3 to
2 and when I picked it up from them
the CEL came back on. I've changed
coils 2 and 3 and all plugs and it still
has a rough idle and CEL

5 Answers


our engine light flash?? thats a sighn of a misfire a bad coil, or plugs

2 people found this helpful.

What did the plug from the misfiring cylinder look like? Was it wet from gasoline? Wet from coolant? Dry and black? Wet and black? - Jim


No other codes indicating a IAC sensor?

1 people found this helpful.

Dirty throttle bodies. Usually cleaning them smoothes out the rough idle from what I've been told. I have the V8 model so it's not an issue for me.

1 people found this helpful.

I have a 2005 Colorado with the 4 cylinder engine that I've had for 11 years and it's been a great little truck. It has just less than 200K miles on it and in the last year or so the idle at start up and when coming to a stop had gotten worse and worse. I tried a number of things to fix it but nothing worked until I found on the internet about the the dirty throttle body issue. So I took off the throttle body and cleaned it up with throttle body cleaner and a tooth brush, buttoned it back up, torqued to specs, etc. and WOW what a difference! It was like having a brand new motor I shit u not! So if you have a rough idle on a truck with a lot of miles on it and you've tried the obvious things like a tune-up, new fuel filter, and it's still got a rough idle, then clean the throttle body. The difference is nothing less than amazing.

2 people found this helpful.

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