Misfire Cylinder 5 - 2010 Chevy Silverado 6.2

[1972C10]

I'm new to the forum and looking to get some advice and next steps on an issue I'm having. 

 

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

 

Issue: I'm having a misfires 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. 

 

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 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 
• 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 10k miles. 

Edited September 21, 2022 by 1972C10

[richard wysong]

compression test all cylinders, why didn't you swap coils with cyl 5? A bad camshaft will cause those symptoms , did the valves appear to be opening the same amount on cyl 5 as the others on that bank? what are the code definitions other than the misfire codes? Possible carbon build up on the valves

Edited September 21, 2022 by richard wysong

[1972C10]

Sorry, that was a typo on the ignition coil swap. Should have been cylinder 5 instead of 4 (OP edited). 

 

I'm wondering if the previous owner replaced a bad lifter but didn't replace or inspect the cam for damage.  

 

Valves did appear to be opening the same amount on 5, but that was also in park on a cold engine. I'm getting misfires in drive at idle.

 

Updated the post with code definitions. 

 

I think my next step I'll do a compression test. If that checks out and nothing abnormal, then I'll inspect the intake gasket and run a can of seafoam through it. Today while driving to work it was misfiring but not as bad. Not enough to throw a CEL or store a code. It's odd how random it is. 

[SC Dean]

I had a similar situation with my 2008 5.3. Ran beautiful on the highway but then, at a stoplight, it would idle rough and throw a cylinder 2 misfire. Hard shift from 1-2 on acceleration then it would smooth out and run good again.

Compression test showed bad compression on cylinder 2. Get a leak down test done too. The head was pulled and found to be a bad intake valve seat. The head was rebuilt at it runs perfect again.

[swathdiver]

Get a subscription to the shop manual at AllDataDIY and resolve the P2270 code first.