My 2000 Superduty with the 5.4 idles too fast all the time.

In park, fully warm, on the tach it shows what I would guess to be 1200 rpm. Idles in drive @ 1000rpm.

There are no vacuum leaks, 100% sure. Been checked and rechecked.

The motor runs fine, just idles way to fast.

Any ideas?

 

Have you checked for a intake leak? Crack in the plastic seams?

 

Nope

I just had a new intake manifold put on it, due to a coolant leak on the right front, where the aluminum coolant crossover passage bolted to the intake.

The idle problem was there at this time also.

Thanks