P0303 Cylinder Misfire

[rick619]

2023 Bighorn with 5.7. Bought new in April of 2024. Currently 10K miles on it.

I was driving at slow speed on the street last weekend and the truck started shaking almost like it was running out of gas. Check engine light flashing. I was down to about 1/4 tank, so filled it up, but didn't help. Took it to the dealer Tuesday. They called yesterday and said they were showing cylinder 3 and 6 misfire. Said they were going to try the spark plugs first. I asked the service rep if it's normal for a truck with 10K miles to need new spark plugs? He was caught off guard, and said 'maybe'. I didn't press him further figuring he is not the tech.

I've done some research and found it could be a few items:

camshaft
bad fuel injector
defective coil
failed lifter

Some with 4th gen that had the engine replaced.

Please chime in if you've had this issue. Luckily under warranty, but discouraging at 10K miles and pretty light use.

 

[js12929]

just came up today, p0303 cylinder 3 misfire detected. 2019 Laramie 5.7 Hemi with 46,700 miles

 

[PurpleRT]

I’d start cheap and easy throw some fuel injector cleaner in the tank and put some miles on her. Could be a gunked injector.


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[rick619]

Got mine back from the dealer Thursday. They tried spark plugs first (didn't help). They ended up replacing the injectors in cylinder 3 and 6.

Not sure if this is likely to be a problem in the future? Doesn't seem normal to have this issue at 10K miles.

 

[PurpleRT]

Might just be bad gas causing a gunked injector. I wouldn’t just assume the worse lord knows Im sure the dealer is wanting to jump right into saying it’s cam/lifter issue etc. Try the injector cleaner!!


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[shayram]

Happened to me a couple of month ago. Dead fuel injector. 21 model with 54,000 miles.