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Idle pulsesating

Jmac42

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2005 Duramax HD 2500, 6.6 diesel has had fast idle and is noticeable in gear at stoplight, over summer travels I have noticed the fast idle is pulsating and becoming an issue. I’m good at on gas engines, not much experience on diesel. Look forward to community’s help. Thanks.
 

RI Chevy Silveradoman

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Maybe you have a bad injector???
You can check the balance rates with a tech 2 scanner.

Any CEL Codes?

Welcome to the forum!
 

btfarm

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If I remember correctly there was a surge problem with LLYs that involved a reflash needed. I had my 05 reflashed for that issue when I owned it. You might ask at the local dealership. Assuming, of course, that you have a stock tune in the truck.
If not then a better aftermarket tune might be an option for you.
 

THEFERMANATOR

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What is the temp gauge reading? It should be idling at 680 rpm's when up to temp(the gauge shows just shy of 210 once it reaches roughly 175 degrees for most clusters). There was a flash for a touchy uncontrollable pedal at parking lot speeds, but most put a stiffer spring on the actual pedal to help with it. Another semi common issue is the spring in the fuel regulator begins to fail and your rail pressure hunts up and down rapidly giving an idle that hunts/pulsates with the rail pressure changes. If your idle is faster than 680 rpm's, then you could have an issue with your coolant temp sensor or it's wiring giving inaccurate temp feedback to the ECM that messes with the idle speed.
 
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