2001 5.0 engine revs uncontrollably

[merrillf]

While coming to a stop my engine began to rev to 4000 rpm. I was able to step on the brake and hold it while I put it in park and turn off the ignition. Waited a minute, started it and everything was normal. No check engine light so I assume no codes set. This could get very serious

 

[my98nnj]

Check your floor mat.
Make sure your throttle cable isn't binding up.
Check the throttle return spring.
Check the throttle body for binding.

 

[koda2000]

as someone had posted resently, check the spot welds on your throttle pedal bracket where it's mounted to the firewall. they have a habit of breaking. it might also be a bad TPS if the pedal and the cable checkout ok.

 

[BubbaFL]

it might also be a bad TPS if the pedal and the cable checkout ok.

How could a bad TPS could cause that?

The only way the engine will rev that high is if more air is allowed in - either a big vacuum leak or throttle being opened (stuck pedal, cable, bad spring, or the cruise control seriously malfunctioning).

 

[swetrid]

Iac valves stick on 5.0L

 

[patrick112390]

Iac valves stick on 5.0L

yea, but even if the duty cycle was stuck wide open at 100% it would only raise it to around 2000

 

[koda2000]

re: TPS. I don't know how a bad TPS can cause this problem, but I have another vehicle (granted not a Ford) that this has happened to twice over the years and it turned out to be the TPS. another thought I had was a sticking throttle body butterfly. they can get loaded up with carbon and not want to return to the closed/idle position, but 4000 RPM seems high for either situation. sounds more like a pedal/cable problem.

 

[yavapaires]

I agree. There are not very many people out there that lube the throttle cables. Also don't forget the cruise control. If it gets a signal, it COULD open the throttle un expectedly. To properly lube the throttle cable, you will need to remove the cable from the throttle butterfly, just prys off. Look for a small hole in the plastic near the end of the cable. Hold cable up and spray into the small hole. You will need to do this every month or so until the cable is lubed. Don't forget to lube the cruise cable too.

 

[swetrid]

yea, but even if the duty cycle was stuck wide open at 100% it would only raise it to around 2000

You would think that but I have seen much higher over the years. I have seen alot of weird crap over the last 17 years at Ford.