Ford Mustang

I have a 2000 Mustang GT with 122,000 miles. At 4,000 RPM's I am getting a bad pinging (detonation). Does not matter if I am at WOT or not. It has been doing this for some time now.

So far I have replaced the computer, fuel pump, MAF Senso, cleaned my K& N Air Intake, have ran some Injector Cleaner through it and I only run Supreme (91 here in AZ & I have tried adding Octane Boost).

Also, when the A/C is running idle sits at 750rpm's, jumps to 1,100 and settles back down to 750.

Any thoughts or reccomendations?
March 3, 2006.

Your timing may be off. A throttle position sensor might fix the idle problem. I believe the stock timing for mustangs is 10 degrees ( I own a 92 5.0 and thats the stock timing for it)

Mar 4, 2006.
Could be a bad knock sensor. It's supposed to retard the spark a little when it senses a knock.

The idle rpm may just rise and fall as the A/C compressor cycles.

Mar 14, 2006.