2000 F150 4.6 High idle then no start
 

Have had on and off problems with high idle for about a year. Replaced IAC 6-8 months ago and it fixed it, but 2-3 months later high idle came back. Found if I romped the gas pedal to the floor and released it idled right back down! In the past year I have had to do that 3 times only.

Today pulled into a parking lot and had high idle as I came to a stop. Mashing the gas pedal trick no longer worked (figures...) and shut it off. Now wont start at all.

Had to have sister in law tow strap me home. Seemed like it was fuel related (new pump 12 months ago) so put the fuel press gauge on it and it goes up to 40psi and holds while cranking. So pump is working.

Read through a few posts. THe high idle could be TPS, ECT, ACT, intake gaskets, vacuum leak.

Have made visual insp of vacuum lines including brake booster-all look good.

Right now my primary problem is no start. (hot). Will try cold start in the morning.

I'm guessing crank and/or cam position sensor...any help greatly appreciated...

Also, someone told me that the ABS sensors in the hubs could cause a high idle if faulty. I pulled the rotors and cleaned both front ring sensors a week ago just for GP. But have not replaced the hubs.


Went out this morning after it sat all night-started right up. Shut off and started again. Idle was normal.

So will see if it fails again when hot. It absolutely would not start at all last night when hot.

Took it to the autoparts store to get scanned. No codes other than the fuel ckt fault I caused when I pulled the fuel pump relay to check the pump manually. Starts fine when hot now. Don't feel the truck is reliable anymore though...I'm very open to suggestions...