Rough idle

CHARLIE GAJEWSKI

MEMBER
2004 CHEVROLET TRAILBLAZER
4.2L
6 CYL
4WD
AUTOMATIC
150,000 MILES

We had two days of 20 below zero weather. Tried starting did not start. When it got warmer out started it and runs very rough and less power than before. Tuned it up still no help. Got a milky residue inside air intake and on butterfly on carburetor.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,867 POSTS

Hi and thanks for using 2CarPros.

The residue you see is most likely the result of condensation created by the extreme cold and then warmer weather. How much fuel was in the tank? Has the check engine light come on? If you clean the throttle body of the residue, does it make any difference? Is the air filter dry and in good condition?

Here is a link that discusses a rough idle, possible causes, and how to fix them. Take a look through them.

https://www.2carpros.com/articles/engine-vibration-at-idle

Next, if the check engine light is staying on when the engine is running, here is a quick video that shows how to use a scanner to retrieve diagnostic trouble codes.

https://youtu.be/YV3TRZwer8k

I realize most people don't own a scanner. If you don't, most parts stores will scan it for free, so have that done and let me know what codes are found.

Start with these things and let me know the results. Also, if you have already done these things, let me know what you found and if any additional diagnosis was done.

Take care,
Joe