StonedCL

iTrader: (1)

Does anyone know what would cause the car to misfire every week then reset itself?
I know a bad coilpack would cause this , But i did have a bad coil in the past and car was shaking like crazy would not go over 50MPH the coil pack was fried! This time car drives fine just misfires every week or so. All the coilpacks where replaced and spark plugs where replaced about 40-50K miles ago with the OEM ($12 each) spark plugs. The car has CAI , OBX headers and outlaw IM and TB spacers. The new owner also just changed the CAT on the car cuz it was making some noise so also has a NEW cat. The IM and TB was scrubed down and cleaned about 20K miles ago, car was well maintained and oil changed with Castrol GTX high miliage every 4-5K. I am stumped, Like I said car drives fine, no shaking just shoots a CEL light for misfires, sometimes just cylinder 1 and random misfire and sometimes 3 cylinders.. What could be the root of the misfires?

BTW the car has about 175K miles..

NSXNEXT

iTrader: (2)

Plug not tight?
Has he pulled the plug and looked at it?
coilpack loose/poor connection?
I always spray the connection with contact cleaner before I reinstall.

StonedCL

iTrader: (1)

It does not seem to be the coil pack cuz I replaced the coilpack for cylinder one 2 times, once with a used coilpack and once with a new coilpack with no luck, still misfire from same cylinder 1.. The plags are not old only about 40K miles on them and it didnt start to happen till about 30K miles after the plugs where put in.. Could one come loose on its own?
Anything else anyone can think of?
I will see about changing the plugs again but can anyone think of anything else?
Thanks for the help NSXNEXT, I did not spray the cleaner but did use the electric grease.

n0rm

iTrader: (6)

I thought you sold your car, your sig says so?

NSXNEXT

iTrader: (2)

And Stoned, dielectric grease works too.

StonedCL

iTrader: (1)

I did but I am going the extra mile and tring to help this guy out that bought it... I started happening to me every week or so before I sold my car . I though it was the coil packs So the guy replaced all the coil packs and he replaced the Cat and is still having the problem, So I am tring to figure it out for him... I guess im just a nice guy

ChucksCL-S

Might need to look deeper, intake or exhaust valve, or piston? Leak down or compression test will verify those three possibilities.

StonedCL

iTrader: (1)

I don't think it is anything major, car drives great.. It does not keep misfiring it seems to just misfire once and thats it causing the CEL light to come on but it will shut off after about 50 miles.. Then it will misfire again a week later same thing but it will not keep misfiring...

phee

iTrader: (5)

When is the last time the car had an adjustment? Sounds like valves me be the culprit. Over time the exhaust valves get tight and the intake valves get loose. More air gets in and less can get out. This filled the cylinder with burn exhaust gasses and causes misfires because thr temperature is so high the fuel pre ignites

phee

iTrader: (5)

If it were a coil pack or plug it would misfire on all or 3 cylinders most of the time. Not just 1

StonedCL

iTrader: (1)

I had the valves adjusted about 5 years ago 80K miles ago when I had timming belt and water pump done./