Just changed all 4 sprak plugs today. They were pretty burnt. 25k miles.
Installed new NGK 5476. Everyone said they come pre grapped. Seem to be around .35

Issue before was backfire (would pop a few times) under WOT only.
Issue now is under ANY pressure the car while completely studder and barely go.

 

Neve heard of that plug for a Cobalt before... Could be your problem. NGK Cobalt plugs start with BRK or ILT...

 

they are ILTR5D 5476

 

Those are the stock LNF plugs then. Should be pregapped and good to go. Don't know what's up then. Sorry.

 

double check the gap. even though they say pre-gapped, you should always double check the gap before you put new plugs in just to confirm. also if you've done mods then your gonna have to play with the gap a bit to find your motors sweet spot.

 

^^^ true story ALWAYS check!

 

They were all gapped to about .35. I changed them to around .31 and nothing changed.
What to do... take it to dealership? im tired of doing this ****

 

well what motor do you have and what mods do you have? i know someone mentioned LNF earlier but confirm that that is what you have.

 

well u have a bad plug then if u changed them and now u have issues

 

yup. LNF. zzp tuned. zzp intercooler, pipes, intake.
They were brand new plugs. Ill try another set i guess.