Huckleby

Hi all, I have a 2011 GMC Sierra 5.3 LC9 (AFM deleted) with cold air intake. Lately it has developed a stumble on initial cold startup. runs fine otherwise. I have cleaned the throttle body at each oil change along with the MAF sensor. Any ideas?

Final Update: I was wrong. I found that my coolant was disappearing internally and upon further investigation found a blown head gasket on #5 cylinder. I tore it down, milled the heads and reassembled with new gaskets and bolts. It is now running strong as ever.

I have a Volant and I like it.

I had the exact same problem. I was running Fram oil filter and read somewhere to change to the AC Delco filter. I did and it fixed my issue. I think the Frams must be a little too restricting.

Okay I think I may have a diagnosis. I think I have a fuel injector stuck open on cylinder 5. I recently replaced the intake gaskets and when I went to relieve pressure from the fuel rail, nothing bled out. I think the injector is flooding #5 with fuel causing an occasional hydro lock condition and also a rich mixture at startup. Ordered a set of new injectors this morning. We will soon see!

Update: After a recent episode of failing to turn over I checked the positive battery cable and starter motor and found that both were hot. I figured the starter was causing too much amperage to be drawn from the battery so I replaced the starter. New starter seemed to crank a little slower than normal and within 5 start cycles the truck again did a failure to crank. In the meantime right after one of the successful starts during a rough idle it gave a P0305 code. This, after I had traded coil packs with another cylinder (so I know it’s not the coil pack anyhow). Could cylinder #5 be hydro-locking, causing the failure to crank at times and rough idle on startup? Thoughts?

I have a 2011 GMC Sierra 1500 with the 5.3 liter LC9. Lately I’ve been experiencing at initial start up, a failure to turn over condition. (Like a dead battery) After several attempts to start it will turn over and start almost normally. I do not believe it is voltage or battery related. All connections seem fine. Once started the engine has a rough idle for the intital couple minutes then Smooths out. Occasionally it will throw a P0300 or P0305 code. Once running it starts and run fine. I do notice vapor from the exhaust when it runs rough and a smell that I can only describe as like an electrical burning smell.