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2003 Chevy Trail Blazer idles rough

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Feb 26, 2015, 5:14 PM

Post #1 of 2 (1003 views)
2003 Chevy Trail Blazer idles rough Sign In

I have a 2003 Chevy Trail Blazer with 170,000 miles, 4.2l engine. I had the engine light come on months ago at different times and had to replace coils 5 then 6 since that had happen I had trouble with the blazer running rough or stalling when I would turn on the AC or go to a stop with the AC on. Hammer Time Suggested Cleaning the Throttle Body, I did as suggested and it help alot it stop stalling but it hasn't been running the same ever since the first coil had to be changed. When I come to a stop the blazer idle is rough even when I put it up into neutral their is know difference in engine speed or sound the same happens if I turn the AC on or off when the clutches engages theirs no engine shift. 1 of my 2 question is would and should I replace the remaining 4 Coils 1-4? would that help?. Question 2 do I need to get a deep scan of the blazer to see if their is some codes I am not seeing with my inexpensive scan tool, can it be an air/fuel mixture problem. please give me some advise. Thxs.

Hammer Time
Ultimate Carjunky / Moderator
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Feb 26, 2015, 5:27 PM

Post #2 of 2 (1000 views)
Re: 2003 Chevy Trail Blazer idles rough Sign In

You definitely should scan the system for codes. That should always be the first step. As far as the idle changing when accessories are turned on, don't expect to see any change. The computer will automatically compensate the idle speed to maintain the proper RPM.

You might want to remove the EGR valve and make sure there isn't a chunk of carbon holding it open at idle.


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