1999mustang2000

changed the plugs and thermostat..now when i rev the car let the rpms come down a little then rev again it pops real loud in the exhaust

devongarver

Sounds like its backfiring, unburnt fuel in the exhaust is igniting...

WhiteFoxGT

backfiring thru the intake or exhaust? Are the plugs tight? Did it blow a plug out? Anything is possible

89gtwith3.55s

headers could have a loose bolt too

1999mustang2000

plugs are tight but i did have a bad o ring when i started the car and fuel squirted out a little so im not sure if maybe some got down in the plugs or if maybe some of the coolant got in them from where i changed the thermostat..


and backfiring through the exhaust

1999mustang2000

ok got the backfiring stopped but now it misses like crazy

fisher2985

was everything good before u changed the plugs?

1999mustang2000

yea it had a little miss before

fisher2985

u probably got a bad coil then. if the check engine light is on take it to advance. (they will scan it for no charge) any code between a p0300 and p0308 is cylinder misfire. (ie p0304 is cylinder # 4 misfire. then u will know which coil or coils to look at. also what type of plugs did u use?

1999mustang2000

autolite double platnum