I HAVE A E-150 WITH A 351 CI..I WILL BE SITTING AT A RED LIGHT AND ALL OF A SUDDEN THE ENGINE WILL REV UP AND I CAN GO DOWN THE ROAD 50 MILES AN HOUR..SCARY..SOMETIMES IT WILL RUN FINE FOR A COUPLE OF
IT GOES 50 MILES AN HOUR WITH OUT PUTTING FOOT ON GAS PEDDLE..I HAVE WORE OUT 2 SETS OF FRONT BRAKE PADS IN 3 MONTHS..
The model year will help us determine what might be happening.
Is the "Check Engine" light on or have you checked for any codes? The first thing I would suspect with a high rev like this is a vacuum leak. There's the possibility of an Intake Air Control (IAC) Valve malfunction. Ford had some pretty weak PCV and Evaporative Emissions hoses too. I'd start with the PCV system - check every hose and elbow for collapse or splitting. 2 sets of Front Brake Pads in 3 Months is a lot but what about the rear shoes? Usually, a Ford Van will wear out brakes 2 to 1. In other words, 2 sets of fronts to 1 set of rears. I suggest you look for vacuum leaks and check the Diagnostic Trouble Codes. Once you get the RPM's down, I'd take a good look at the rear brake operation. P.S. - I do not recommend driving a vehicle in this condition.
Sounds like the same problem my 1995 5.8 liter 351 had with a high idle. I replaced the throttle position sensor and it solved the issue. I now idle slow 3 mph down the road instead of 37 mph.
The IAC Idle air control valve is very popular. You need to also inspect the accelerator linkage for any worn bushings which are plastic. Something may be catching off and on
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