Hello, I'm new to the forum and have a question on my truck misfiring.

I have an '06 with 97k and was experiencing a misfire around 45 mph when shifting to OD. A friend suggested that it was either a plug or a coil pack and since it was time to change the plugs I'd start there. I had new plugs installed and it seemed to smooth everything out. Only a couple of days later the truck start to miss badly while accelerating at all speeds. Shuddering and chugging terribly. So next I had a friend run a scan to see what cylinder was missing. The error code was #3 so I changed the coil pack on that cylinder. The problem did not go away. I'm running out of ideas. Could the new plug in that cylinder be bad? Any suggestions would be helpful. Thank you

 

Did you use dielectric grease while reinstalling boots? The boots probably needed replaced as well. Also, sometimes a new plug is cracked when it is installed.

 

Other general maintenance, has the fuel filter been changed in the last 30,000 and have the MAF and throttle body been cleaned.

 

I had a mehanic change the plugs. I changed the one coil pack and did use grease. Sounds like the fuel filter is due to be change.

I think I'm going to inspect the new plug in that cylinder that had the error code.

 

Are you sure you are looking at the right cylinder? #3 is the 3rd one back from the front on the passenger side. It ain't numbered like a Chevy!