weird intermittent limp mode issue HELP

adam12345

New member
Feb 19, 2022
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06 GMC Sierra 2500hd 4WD LBZ stock, lift pump, 147k miles.

Long post but please bare with me. So there is a strange thing that happens with my truck ever since I got back from a boat trip. The truck had been sitting for about 3 months in my garage and since I’ve started to drive it again, at about 140 degrees coolant temp, fuel pressure drops and truck bogs. Throttle response is little to none and when you go pedal to the floor the truck jerks until you let off. This issue goes on until 144 degrres coolant temp. I usually have to pull over and come to a stop for it to go back to normal. The truck is not starving for fuel, desired and actual are spot on, its the desired*** fuel pressure that drops. Also it usually seems to happen in 5th gear unlocked. NO CODES. I’ve replaced my fuel filter and have done a decent look over on the truck but it does not seem like a mechanical issue. Anyone have some input on this? I’m stumped and its getting kinda dangerous especially when you have no power going 40-50 mph. Thanks
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
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Norcal
all stock or did you do anything with the egr? can you log the MAF air flow when it does it and see if it drops a lot?
 

adam12345

New member
Feb 19, 2022
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1
all stock or did you do anything with the egr? can you log the MAF air flow when it does it and see if it drops a lot?
All stock. EGR is still installed and plugged in. I’ll be driving the truck later so I can look at MAF value. Thank you for the suggestion
 

Ron Nielson

Active member
Oct 11, 2009
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Berryton, KS
And check your air filter also. Amazing how dirty those things can get. Are those coolant temps you posted from the dash gauge or something else?