Hey, first timer here. I have an 02 mustang v6, has been minorly wrecked twice. After awhile it started running bad around 70k miles, i have put new plugs in it, Bosch Platinum +2's and it seems to have made it worse, i did not change my spark plug wires. i have a K&N airfilter, hasnt been cleaned in awhile, it is bone stock, was tuned but got reset after batter change. At idle it is smooth then out of nowhere a big vibration, and goes smooth, just contiunally does that. When i rev the engine it revs fine then when i let off the gas it seems to wanna backfire very quietly, its very odd. I recently changed the fuel filter too, and ran lucas engine cleaner in it. Help please! The miss is agervating and seems like my fuel mileage has went down.

 

when u rev the engine and let off, it's normal to hear a lil bit of a "popping" sound, kind of a light rumble. but if ya hear a blatent backfire, like a firecracker, that prolly isn't good.

 

ok i am a young tech at a big ford dealership in kansas and i have seen this problem once or twice. i would start with going back to the motorcraft spark plugs you know thats what the motor likes for sure and the second thing is the K&N filters have a oil on them that are bad on the hotwire of the MAF ( mass air flow) and the AIT( air intake temp) this can cause your motor to be reading a warmer air intake temp because the oil on the hotwire will retain the heat from the hotwire and the thermistor of the AIT I hope this helps with the problem keep us updated

 

i havent checked this post in awhile, but i a local friend that works with mustangs and he said to use motorcrafts that mustangs hate boschs. so that may be it. at advance is says cylinder misfire 1 and 2. but it doesnt miss all the time, it revs smooth, but going down its like bom-boom-boom and shakes alot but does the light rumble. idk, i want to rev my car and it be smooth down. lol but ill try that