High RPMs at stat up with AC on

[flbeachbum]

I have had this issue since 70K miles. Only with the AC on the RPMs go to ~3500 the truck is slow and the engine sounds like a BIG desel truck. After 2 mins or so the RPMs come back in line and the noise stops.
Ford dealers can not find a problem. Can anyone out there help?
Thanks All

 

[Tech By Trade]

You could try taking the belt off the AC compressor and fire up the truck for a second. Flip on the AC and see what happens. If doesn't do it either the clutch or the compressor are dragging the engine down and need to be replaced. Either that or you have a lack of power somewhere and the extra power taken up by the AC is exaggerating the issue. Was the shop able to pull any codes?

 

[flbeachbum]

You could try taking the belt off the AC compressor and fire up the truck for a second. Flip on the AC and see what happens. If doesn't do it either the clutch or the compressor are dragging the engine down and need to be replaced. Either that or you have a lack of power somewhere and the extra power taken up by the AC is exaggerating the issue. Was the shop able to pull any codes?

Thanks Tech by Trade.. There are no codes. I'll look into your suggesstions. The problem never happens when I have the AC turned off. So the problem is, as you suggest, in the clutch or compressor.
Thanks agin..