Hi i have a 2002 f-150 4.6 2wd, and for the past month, when i start it up goes to the max rpm then goes to 0 and then goes to a normal rpm (about 650). So this past tuesday i started it up, it did as i described above, then thepms rose to 2000 rpms, it then started going back up, i kicked the gas to see if it would drop, it dropped back to 1900 and stayed there. I then shut the truck down and restarted, it stayed at 2000 rpm for another 5 mins before going to normal ( about 650)..

I havent changed the plugs, i bought it in aguest of 2011, no real problems till now, any suggestions will be greatly appreciated..

thanks Michael

 

Higher probability candidates are IAC valve and fouled throttle body. Does this happen in frigid temperatures?

 

Sounds like IAC is sticking.

First, remove throttle body. There is a screw coming in from the back side that holds the throttle plates open (slightly). Usually this screw is inserted, then the head is broken off so you can't mess with it. Tae some pliers and remove this screw completely, replace it with on that you cn adjust. IT'S METRIC !!

Now, clean the inside of the throttle plate, the blades etc. DO NOT get anything into the sensor on the side. Spray carb cleanr on a rag and wipe till all is clean.

Re-install. Unplug IAC, start truck and let it wrm up. Set base idle (turn screw) so truck idles nice in gear about 550 RPM. . Shut it off.

Disconnet battery, REPLACE IAC.

Bolt on IAC, hook up battery, and enjoy.

 

IAC.... 10-15 minute job. Clean the area where the gasket goes before putting it on. check for coupon codes on Advance autos website. I just got a new IAC for 30$