hello all,
i have a 2004 F150 super cab xlt with 4.6. i bought it with 23k miles and now has 210k miles.
few weeks ago i figured i'd give it some love. changed oil, spark plugs, removed and cleaned throttle body and maf.
since that very moment every time i start it the motor revs up to almost 2000 rpm's and then goes down to normal. runs and idles just fine after that. it didn't do that before.
i'm pretty sure my tensioners are bad because it makes chain noise for a couple seconds until it builds oil pressure but that's another story.
what could be causing this sudden rise in revs on start up?

 

what did you clean the TB with ??

 

i cleaned it with crc throttle body cleaner and the maf with crc maf cleaner

 

ok...that's good. you used the proper cleaner. got to be the TPS..maybe got TB cleaner in it.

 

anything i can do about that?

 

It's mounted on the side of the throttle body and pretty sure you can replace it..sounds like it's holding you throttle high at start up and then with the choke kicks off your good. maybe somebody that has had this same problem will chime in...

 

When this happened to me after cleaning the throttle body on my 2004 Mazda 3 simply disconnecting the battery for an hour or so fixed the issue. I read that the car was still using the same fuel/air ratio for the dirty throttle body so that was affect the idle. May not work on a F150 because when I cleaned the throttle body on my F150 it had no issues.

Just an idea.

 

also had no issue when I cleaned mine...

 

Now that I think of it more my suggestion will not help your issue because my car had a constant high idle even after warming up.

 

i'll check on the tps to see if it's possible something may have gotten in there.
one thing worth noting - while i was cleaning the throttle body i noticed the opening for the egr valve was pretty caked up. looked to me like it should have been a normal round hole and instead was about 70% blocked by what seemed like carbon or something. i gently pried it with a screwdriver and it popped off leaving the normal looking hole for the egr.
may this have done something? could the egr have that effect? does it let extra air into the intake which would make the motor rev high for that second or two?