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High Idle At Startup

Merc570

By Merc570
in Ask A GM Technician

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Merc570 Enthusiast

Merc570

Posted
Posted

I have a 99 5.3L GMC Truck. At startup it will idle high at around 1200 RPM. Once engine warms up it will idle at around 600 RPM. This only happens at first startup or if its been sitting for several hours. The air filter is clean and I have no codes. It happens when outside temps are cold or even when temps outside are in the 70's. I havent noticed anything strange with engine temp on the gage. Any ideas?

 

Jim

pennzoil29 Senior Enthusiast

pennzoil29

Posted
Posted

Good luck. I have a '99 5.7 with a wild high idle issue. Mine turned out to be a faulty ecm. Use the search at the top right hand corner and type in high idle. You will be amazed at how many have had this issue. Hope this helps you.

truck1014 Enthusiast

truck1014

Posted
Posted

Dude... my gmc has been idling high in the mornings for the past 2 years lol its got 185,000 miles and its still running smooth i wouldnt worry about it..!!!

Ranger Senior Enthusiast

Ranger

Posted
Posted

I'd say it was pretty normal, all my vehicles has always idled a bit high after a cold start. I believe it's simply an automatic operation to warm the engine up to operating temperatures (about 210 degrees).

C6Racer Enthusiast

C6Racer

Posted
Posted

Ranger is correct. High idle at startup is normal and is meant to expedite engine warm-up. My 2000 C1500 nbs with the 5.3L idles at around 1,100 rpm during a cold start-up. You've got nothin to worry about my friend. If it idles high all the time then it might be a concern.

RobM Enthusiast

RobM

Posted
Posted

Like everyone else has said, I think this is pretty normal. Don't most cars idle high until the O2 sensor goes into closed-loop?

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