Need Help - pinping noise and revs up

[mustang2002]

HI!

I just purchased a Mustang V6 2002 with 31,000 miles. I loved the car! The problem is that the car has a pinping sound on acceleration (no loss of power) on neutral (revs up) and while driving (acceleration-under load). Also, while driving, if you stop at a red light you noticed that the engine will accelerated itself from around 700 rpms to 1000 rpms for a few seconds and then returns to the 700 rpm range. The previous owner placed a screw on the EGR valve (I removed it). The car has an H exhaust system and headers. The engine runs very smooth at iddle. Spark plug # 3 was also loose and I pushed it back in place. I'm not sure that the spark plug wires are in the correct position.

Spark plus wires and sequence
1-2-3-5-6-4

Thanks for your help!

[a00v6stang]

did you get any warranty on the car when you bought it?

[SpectorV]

if the idle hangs or wont come down when you are sitting still or what not you should clean your MAF sensors, the v6s have an idle decay rate issue and this helps fix it. use on contact NO residue electronic cleaner from autozone, do NOT USE BRAKE CLEANER.

if you are returning to pinging, it may be detonation in, does it sound like marbles in the upper intake?

[mustang2002]

Yes! The engine sounds like it has marbles in it. The MPG is also bad. Engine power is good.

[a00v6stang]

detonation

[SpectorV]

dont rev on it, drive normal get it checked its bad