1991 Ford F150 fast idle

I have a 1991 Ford F150 1/2 ton truck which just started idling extremely fast. The idle speed does fluctuate some (it slows down but then speeds right back up). The engine also bogs down periodically when accelerating. I replaced the fuel filter but that didn't help. Any suggestions would be greatly appreciated.

You might want to check your cable to the throttle body, it might be sticking. or, you might have a bad throttle position sensor (TPS). Does your check engine light go on at times when the truck's running? If so, you can take it to an Autozone Store and they will check it for free.

Vacuum leaks are the most common cause for this. It could be anywhere, but most often it's in the open and easy to find.

Definately. What you describe sounds exactly like a vacuum leak. Check the PCV and Brake Booster first.

that sounds a little like my '92 f 150. I recently had to replace the tps, idle sensor and the coolant sensor just to keep it running longer than 15 minutes at a time. :eek7: It still wants to coast along at 45 to 50 with my foot off the gas pedal tho. But at least it's running :biggrin: Before that it would flood out and shoot carbon out the exhaust, making it look like it was on fire. But for $500 I'm happy with it