Codes P0300 or P0303, Traction control off, service Stabil Trak and check engine light turns on

KINSEYJAMES

MEMBER
2007 CHEVROLET AVALANCHE
5.3L
V8
4WD
AUTOMATIC
201,000 MILES

OBD2 scanner gets codes P0306 twice or P0300 or P0303. I have checked spark plugs, coils, wires, cleaned throttle body, changed out air filter, cleaned mass air flow sensor, wheel speed sensors are okay. The fuel pump is working fine, I can hear it. It's not running lean or no lean code. I notice the misfire in the idle, no reduced power light. I don't know what else it could be. Help

Friday, June 17th, 2022 AT 4:52 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

If the plugs have spark and fuel pressure is within the manufacturer's specifications, that leaves compression, injector issues, or timing.

Other than at idle, do you notice a misfire when the engine is under a load? Also, are you sure there are no engine vacuum leaks? I realize there are no lean mixture codes, but it's still possible.

Is there any smoke from the exhaust? If so, is it dark gray/black, white, or blue? Any strange odors from the exhaust?

Let me know.

Joe

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Friday, June 17th, 2022 AT 9:14 PM