I have had an enine growl / howl problem that seemed to disappear with the cooler weather. However, turning the A/C back on yesterday, the growl/howl re-appeared. Is the A/C compressor bad? A/C clutch bad? Need help. Heading out on a long distance trip at the end of the month... Thanks.

When the moan/ groan comes from the engine bay intake area, I have to back off of the throttle in order to re-accelerate... Gas pedal seems to become dead...

 

That's an interesting problem. A bad a/c compressor can certainly make a growling sound. They will also increase drag on the engine because the excessive drag from worn internals. As for your accelerator going "dead".....not sure about that, almost sounds like two separate problems. The 04+ 5.4 were drive by wire, it's possible you have an unrelated issue with the signal from the pedal assembly. If your a/c compressor is defiantly the growling culprit I'd start there.

 

When the A/C is on, the moaning sounds only happens under a slight acceleration or with the cruise control on a slight incline on the highways... Not a constant/ continuous moan. Just when accelerating... It almost seems like the engine doesn't have the power / brain to either downshift or increase fuel flow to compensate as required...

 

When the A/C is off.... the moan is very slight and the engine seems to correct or downshift as needed.

 

Sounds like this thread maybe...

Bog down moan sound issue solved! - Ford F150 Forum - Community of Ford Truck Fans