2002 Chevrolet Trailblazer Engine running rough

2002 CHEVROLET TRAILBLAZER
183,000 MILES • 4.2L • 6 CYL • 4WD • AUTOMATIC
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THELEGEND017
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It was sitting and idling in the driveway one day and suddenly started running very roughly. I thought it may have been bad gas because I had just filled up, but I have refueled twice since then. Is this a sensor issue or something else?
Apr 17, 2015 at 9:46 AM
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JDL
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Is this rough idle intermittent or does it happen every time it idles? If intermittent, can be hard to track, you have to test when problem is ongoing. The basics for rough idle, check for a leak of some kind, fuel--egr--vacuum. Check and clean the throttle body and anything that has to do with idle air system. Check for applicable trouble codes, If misfire for a particular cylinder, the code should tell you which cylinder. Some of the national brand autostores will check codes for free, otherwise, you need an obd2 code reader at least to check codes, yourself.
Apr 17, 2015 at 10:29 AM
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THELEGEND017
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The computer says random/multiple misfires. It's a constant thing and now my cruise control is gone too.
Apr 17, 2015 at 8:20 PM
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JDL
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Just about anything can cause a p0300. I was hoping it would be cylinder specific, no luck there.

Use a gage and check proper fuel pressure. Also, see if pressure will hold for a bit with everything off, If the pressure drops like a rock look for fuel pressure leak.

Next I'd check your ignition system, how long since a tune-up?
Apr 18, 2015 at 11:24 AM