Newbie here, just want to thank you in advance for any suggestions or solutions. First I want to say that I am as close to being a mechanic as I am to being an astronaut so please bear with me. I can change oil, plugs, filters etc, basic shade tree stuff, if I'm not comfortable doing something I turn it over to my mechanic. With that said, I have a 2002 Silverado 2500 HD , extended cab with the 8.1 vortec. 121K miles. Well maintained, every day driver. I LOVE MY TRUCK! Ok about 10 days ago the check engine light flashed for about 3 or 4 minutes then went off. When I got home I put the scanner on it and got a P0306 code (misfire cylinder 6) in the pending section. Next day after doing some research I changed the plugs ( they were about due anyway) and I also changed the coil for that cylinder, cleared the code and drove it , and after about 40 miles the light flashed again for a few minutes, then went off, same as prior to changing the plugs and the coil. Checked with the scanner and same pending code, PO306. I swapped the plug wire for cylinder 6 with cylinder 4 , cleared the code, hoping the code would follow a bad wire, drove it to and from work, about 50 miles and it was fine until about 2 miles from home and again, flashing check engine light, then it went off. Checked with scanner and still read PO306, so I'm guessing it wasn't a bad wire since the code stayed with the same cylinder. Assuming the next step would be an injector issue ( am I wrong assuming this?) I filled up my tank and threw in a can of Lucas fuel injector cleaner, hoping for a miracle, so far I'm half way through that tank of gas and still the same issue. It is very intermittent, some days it's fine all day, next morning the light will flash and then go off, light never stays on permanently. The only issue I notice while the light is flashing is if I'm in drive and at a light or stop sign I can feel it run slightly rough, normally I cant feel anything at all, it runs very smooth. No hard starting issues, no stalling, no hesitation. What should my next move be, bring it to my mechanic? I am a paycheck to paycheck kind of guy so I try and figure it out myself first but if you guys think it's time for a professional then that's what I will do. Any help or suggestions are greatly appreciated and thank you all for your time.

 

P0306 is a cylinder #6 misfire. Check cap and rotor. Could be a fuel delivery issue as well.

 

Swap the #6 ignition coil with the #4 ignition coil and see if the code changes from P0306 to P0304. If it does, then the ignition coil is bad. Yes, new parts can be bad out of the box. If that doesn't solve your problem, you'll need to do a compression check to see if you might have a valve issue.

 

I hadn't even considered the new coil could be bad! I'll try that today, thanks !