2004 Mustang GT with weird idling problems.
Hey guys I recently purchased a 2004 Mustang GT with 82,000 miles. The engine runs great but often when it's stopped completely the idle dips down to between 600 and 900 rpms and sometimes just dies alltogether. But this doesn't happen every time I drive it, sometimes it's fine.
I've cleaned the Mass Air Sensor and the Idle Air Control and checked for vacuum leaks, all to no avail. The weird thing is that when the car is coasting in neutral it doesn't have any problems but when I come to a complete stop it starts dipping and sputtering.
I purchased this car already with a number of modifications on it. Since I haven't pulled the engine apart I only know the obvious mods which are: BBK cold air intake, throttle body and plenum. It also has straightpipes with no catalytic converters. I'm only mentioning this stuff in case any of this would contribute to the problem.
It was suggested to me to get a Diablo or SCT tuner and see if tuning it fixes the problem but that's obviously a big investment. I wanted you guys' thoughts before I made a move.