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

 

Michael...welcome

DO you have any idea as to what has been previously, maintenance wise??
this really hints of the IAC (Idle Air Control) not operating as it should.

but before that, have you had the codes read?? might be worth doing before we all go dropping suggestions. Even if no codes turn up, it still helps.

 

thankyou first time ive been on here and wil likely hav emore questions later on.

my check engine light has been on since late summer, never thought anythinng of it .. in early december my #8 cylinder was misfiring, re-placed engine coil. and reset check engine light. 1/2 hr later came back on.

now im worried about this , and transmision seems to rev high before shifting gears.

thanks Michael

 

Just to add some throughts, air injestion is the only reason a motor revs up.
I think your due for some maintaince.
First clean the IAC and throttle body.
Then inspect all rubber parts connected to the intake system for cracks, hardness etc that could open up and let air in then close up again.
The normal idle speed is 750.
On cold starts the idle is normally set for as high as 1200 rpm +/-.
Add to that an air leak and things can go well out of control.
Also get some code read and post what the numbers are so we can sort out any further issues.
As for you feeling the motor is revving upon shifting, get the other issues solve first then worry about the transmission shifting.
As it is now you have to many things going on at the same time that will cause confusion.

Good luck.