Help!! Over revving

[KSJim]

My 1996 F53 has started over revving.  It wants to run at 4000 rpm in neutral.  I checked the throttle cable for binding and it does have about an inch and a half of cable left above the pedal.  But the butterfly appears to be closed.

 

[driftless shifter]

Cruise control mal-function? Seen it happen, pull CC fuse see what happens.

Bill

 

[KSJim]

Now if I only new where it was located

 

[Lou Schneider]

If the cruise control was malfunctioning, it would pull the butterfly valves open.

Are they closed when the engine is racing?  If so, look for a loose connection or a missing or cracked vacuum hose that's admitting air around the butterflies.  A fuel injected engine monitors the air to fuel ratio via the oxygen sensor and injects fuel to keep the ratio correct.  More air getting in = more fuel injected.

WD-40 sprayed on suspected areas will reveal a leak as the engine speed will vary when it's sucked in through a leak.  Or you can use a cigar.  https://youtube.com/watch?v=zMok2y05jNE

I had an intake manifold crack on a fuel injected Ford 460 in a work van and it did just what you describe, the engine responded as if the throttle butterflies were stuck open.  Fortunately, I had the presence of mind to shut off the ignition and bring it to a safe stop.  Ford replaced the manifold under warranty.

 

[KSJim]

Update!!  She is running good again.  We had her serviced before our trip, I'll talk with the mechanic when we get home. Turns out that it was a piece of the old filter stuck in the butterfly.  Expensive lesson as we had to call a mobile mechanic to find it.