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2010 Chevrolet Silverado 1500 - 6.2L
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I'm new to the forum and looking to get some advice and next steps on an issue I'm having. I'm running in circles.

Specs: 2010 Chevrolet Silverado 1500 - 6.2l - 124k miles

Issue: I'm having a misfire on cylinder #5, only at idle and when in drive. It will not misfire when in park or when accelerating. The misfiring seems to be a bit random meaning it'll misfire sometimes and other times it'll be bad enough that I get a blinking check engine light, traction control light and stabilitrack service warning. All warning lights will turn off after about 15 seconds or when I accelerate. The other thing I noticed is the truck begins to misfire about 3-5 seconds after coming to a complete stop and idling. It'll only misfire on cylinder #5 when in drive or reverse but not neutral or park.

Codes that it's throwing (using a veepeak OBD scanner):
  • P0300 - Random/multiple cylinder misfire detected
  • P0305 - Misfire cylinder 5
  • P2270 - Heated oxygen sensor (HO2S) 2, bank 1 - signal stuck lean
  • C0561 - System disabled information stored engine speed out of range; system disabled information sotred acceleration pedal position out of range; system disabled information stored transmission gear invalid data.
  • Using the OBD scanner, I can see in real-time when the misfires begin to pick up (about 3 seconds after coming to a complete stop and ideling) and when it's about to throw the CEL.

What I've done so far:
  • Switched spark plug from cylinder 3 with cylinder 5. Misfire still exists.
  • Switched spark plug wire from cylinder 3 with cylinder 5. Misfire still exists.
  • Switched ignition coil from cylinder 3 with cylinder 5. Misfire still exists.
  • Replaced fuel injector on cylinder 5. Misfire still exists. It seemed better for a few days but the issue came back.
  • Pulled the valve cover off and observed for a stuck lifter. No stuck lifter. Started engine to verify lifter worked. Lifter worked.
  • Cleaned MAF sensor just in case. Misfire still exists.

What should be my next steps in diagnosing this issue? I'm thinking compression test. I also have a feeling it could be the intake manifold gasket that is leaking. This is a truck I recently acquired and do not know the service history on it outside of the spark plugs being replaced in the past 8k miles.
 

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Codes that it's throwing (using a veepeak OBD scanner):
  • P0300 - Random/multiple cylinder misfire detected
  • P0305 - Misfire cylinder 5
  • P2270 - Heated oxygen sensor (HO2S) 2, bank 1 - signal stuck lean
  • C0561 - System disabled information stored engine speed out of range; system disabled information sotred acceleration pedal position out of range; system disabled information stored transmission gear invalid data.

What should be my next steps in diagnosing this issue? I'm thinking compression test. I also have a feeling it could be the intake manifold gasket that is leaking. This is a truck I recently acquired and do not know the service history on it outside of the spark plugs being replaced in the past 8k miles.
Solve the P2270 first. It is either a faulty oxygen sensor or a bad ECM. Sign up for access to the shop manual at AllDataDIY for the steps to solve this, pay for a month or longer.

That code sets when the ECM detects that an O2 sensor voltage is not greater than 805 mV when the mass airflow sensor exceeds 550 grams.
 
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