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05 GMC envoy XL 5.3 weird check engine light

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New User

Jul 17, 2022, 6:19 AM

Post #1 of 3 (754 views)
05 GMC envoy XL 5.3 weird check engine light Sign In

I have a 2005 GMC envoy XL V8 5.3 when I accelerate too quickly or stay about 40 mph for too long the check engine light comes on if I back off it goes off the code it throws for is for a number 4 misfire or comes back as a random misfire. No can tell me what the problem is.

Generic codes: P0300 cylinder 4 misfire
P0303 I cant remember if this one is right. This is the code for a random misfire I believe

I changed the injectors a coil pack for number four check the wiring everything looks good I can't figure this out

Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 17, 2022, 2:27 PM

Post #2 of 3 (740 views)
Re: 05 GMC envoy XL 5.3 weird check engine light Sign In

It's been all day with no response so I'm not sure - so you know. I'd have checked plugs or just tossed them didn't see if you touched them or not? Because of picking on one cyl. like that would see spark plug evidence vs another helps and if some miles over the 100k mark just check compression of that one for just way too low?
Oddly only knew of two (chance - alone shop thing) went forever without issue now gone.
Another here said oil getting into plug was common was news to me BTW.
Not sure if fuel pressure would or could set those codes so would check it both pressure and that it holds,


Double J
Veteran / Moderator
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Jul 17, 2022, 6:39 PM

Post #3 of 3 (729 views)
Re: 05 GMC envoy XL 5.3 weird check engine light Sign In

P0300 is the Random Misfire code
P0304 is Cylinder #4 misfire

It sounds like you may have a sticking lifter on Cylinder 4
Common on these AFM (DoD) Engines
Active Fuel Management or Displacement on Demand
In low Engine load, The lifters on Cylinders 1,4,6,7 are collapsed, allowing it to run in 4 cylinder mode
When load is increased, the lifters return to normal .
These use special lifters on those 4 cylinders

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