Engine light on, code P0304

2009 GMC SIERRA
160,000 MILES • 5.3L • V8 • AUTOMATIC
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BASSCHELSEA061
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  • 2 POSTS
Engine light came on, sometimes it just blinks and sometimes it will just stay lit. Gave trouble code P0304 misfiring, and service stabilitrek and traction control light on.
Dec 31, 2017 at 1:07 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good morning.

The 304 is a misfire code for cylinder number four. In most cases, it is a spark plug or coil. How long has it been since you had a tune up?

Roy
Dec 31, 2017 at 1:54 AM
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BASSCHELSEA061
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  • 2 POSTS
Not sure, but I did a compression check and I only have 35 psi on that cylinder and 120 on the other ones.
Dec 31, 2017 at 4:34 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Okay, good find. You have an issue in that cylinder. It is either burned valve or damaged piston. It will require removing the head for inspection.

Roy
Dec 31, 2017 at 4:40 AM
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