well i got my headers and exhaust done and a week after my car started missfireing. so i replaced tha spark plugs and wires with ngk tr-55 and msd's and its still misfireing. its an a4 car and it usually does it when im driving around 25% - 50% throttle and when it shifting into 3rd either right after or before it shifts it will continue to missfire untill i go to 75% throttle and when im at 75% throttle from a get go it doesnt missfire at all........but i noticed when i get on the free way i drive around 75 - 80mph and thats around 2500rpms so after driving above 2k rpms for a while it doesnt missfire at all not even when i drive at 45 - 60 mph unless i stop and when i go it starts it all over again

right now i think it could be

o2 sensor....when we were doing the headers swap my o2 was stuck to my manifold and we couldnt get it off so he gave me one he took off his ta. mine is a 98 and his is a 99 i dont think it makes a diffrence

fuel injectors....they are stock and maybe thier are dirty or my car hasnt learned the air fuel ration yet...the exhaust has been on for around 3 weeks i dont know maybe my car is one of those that needs a tune

my friend blocked off the egr to the head and the intake i still have a ls1 intake, i have a ls6 sitting in the garage but im trying to paint it first...
my theory is that thoir is not enough air going in and too much being forced out....just a thought i still have a stock airbox that will be changed soon

or maybe i didnt install the plugs and wires on right, but i double checked...mistakes still happen

well that what i think, now what about you guys?????

 

what are your plugs gaped at?

 

5.5......should i gap them to 6???

 

U mean .055?

 

oh yea sorry long day

 

That should be fine as long your certain.. I run N20 plugs at .035, its been a long time but I think .055 is fine.

Id double check all wires and make sure you get that "click".. they can be a little tricky.

 

damn i wish i had little gurly hands uuhhuh owell tomarow morning it is thanx man

 

id start there... you throwing any codes? An 02 that is going out or lazy will usually throw some sort of code, or a code that can be traced to an 02.

 

i took of the air and egr so yea, but ill hook it up to the computer in class monday and see

 

yea, you could have another code that you are not aware of.

 

took the car out for a drive today and it only missfired when i first drive it...so i guess it only does it when its cold

 

I would say maybe one of the wires is to close to the headers causing it to arc. If you have the MSD wires, you can bend those a little away from the hearders.
Another thing to check is the gap, it should be .54 - .55 and make sure all the wires have a good connection (specially #8)

 

thanx i will be checking them again tomarow

 

well i just checked them out and the #8 plug and wire was looser than my ex girlfriend so i pulled off all the wires and switched them around #8 being on #1 doesnt click on but it sturdy ill check them again in the morning

 

My car missfired on a .55 gap. I had to gap the plugs to .35 to get it to quit missing.