[stang786]

i thought i solved my problem with the car running terrible. i changed plugs, wires, and o2 sensor because i got a p1151 code. the car ran fine for about a week. i looked up the minimum octane for the car is 87. i ran a full tank of that and justs filled up today with 89. now the car is detonating under full throttle around 4500rpm and up and it was alittle rough cruising in 4th and 5th gear around 2000rm. i pulled plugs from both banks and they are identical, they are both clean with no glass speckles on them. pulled vac on the car its running 20lbs at idle. i checked the egr and iac and they are both ok. at this point im clueless, now the one thing i didnt do was reset the computer after i replaced the o2 sensor. would that cause the car to run the way it is? you guys have been great with advise since i signed on here, im open for any suggestions. please help.

[stang786]

ok found when the problem occurs. it makes sense now when it happens when it rains because of using the defrost. the car detonates bucks and sputters when i use the air conditioning and after i turn it off it still does it. the car runs fine before i use the ac then it feels like there is no power at all after i turn it on and after i turn it on. anyone ever have this happen or know the cause? is the ac vac controled?