I recently changed my wires and plugs. (from delco to ngk tr55) I had a misfire and pop so I checked my wires to be sure they were firmly on. Nothing changed. I then took the driver side bank out and replaced the new plugs with the old plugs. I noticed the second from the firewall #5? was black on the electrode and not white like the other three on that bank. I thought that was the problem and ran the car with that bank old plugs and the other side new plugs. Still had the misfire. So I continued to change all the plugs. All except number 5 were white. But alas the misfire was gone and the car ran great on the old plugs. ( I was changing plugs because my mpg was down from last summer) The new wires are on the car so they seem to be fine with the old plugs so it looks like something is wrong with the new plugs. I checked for cracks in the insulators but can find nothing. I now have the car running good but still have on the old plugs. Anybody with some thoughts on this? Will the car run bad with different plugs only because they are different not broken in some way? I would assume that since every plug has it's own electric source that it wouldn't care if the plugs were different.

 

Both plugs types should be fine! The ngk tr55 are more suited and recommended for highly modified LS engines and will NOT last as long as the GM AC Delco Irridums. The irridums are very good plugs for 75% of C5/C6 owners. Changing plugs from one brand to another will NOT provide and EXTRA HP/TQ! The reason for using the ngk tr55 in modified engines is that they seem to work better in higher compression engines and have less detination.

The OEM STOCK LS engine is not very picky on plugs. In fact the GM LSX ignition system with the AC Delco Irridum plugs is a very good design/combo and works very well and last 70k--80K miles.

I believe that you may not have had a wire on properly or one of the new plugs could have had an issue. CAREFULLY,,,,inspect each of the new plugs for cracks and defects.

I find a LOT of people dont understand that the COIL side of the plug wire need to be properly installed in to the coil for the coil to operate correctly. The metal plug wire connection needs to be located almost FLUSH with the top opening of the coil boot so that it can be inserted into the coil tower properly. You chould hear two distINC "clicks" AS THE METAL COIL WIRE CONNECTION mates with the coil tower connection.

If the coil wire metal connection end is too far into the coil wire boot, there will be an additional GAP for the coil to over come to fire the plug and may result in a misfire or a burnt/corroded coil/coil wire connection.

You also need to make sure that there isnt any trapped air in the coil wire boot when you install the the wire into the coil. I insert a small tie wrap (the flat end) into the boot before I install the coil wire. once the ciol wire is snaped into place, I pull up on the tie wrap (burp out the air) and them pull out the tie wrap. It helps the boot stay on the coil tower.

BC

 

Thanks for the reply! I did check the wires 3 times. Since the wires attached the same on the old plugs and no misfire I believe I have a bad plug(s) with the new set. I thought the color difference on the one plug to be the cause of the misfire but it did not go away until all were replaced. I will probably go get the ac delco plugs and hope for the best. Thanks.

 

I put in new Delco Iridiums,along with new wires, about a year ago and have been Very pleased with them!!(gaped .040)

 

Just bought the AC delco's IR, will be putting them in today.