I have a 2002 f150 5.4 and have it for just over a year. love the truck and enjoy working on it. it's my first domestic vehicle. I do have a quesion to the forum though.one item that annoys me is I have an rpm fluctuation when I am coming to a stop and as the truck downshifts through the gears it pops up about 150 rpm and goes right back to idle level. although sometimes when fast stopping it goes from 4th down to 1st and rpm can go low instead of high. first off, is it normal for the rpms to fluctuate when downshifting when coming to a stop? if this is normal behavior for an f150 then I will stop worrying about it.

 

You may have a sticky IAC - pull it and clean it out with WD-40, work the plunger with a small screwdriver to make sure it's free.

 

I did pull my old one and tried cleaning it out and still did it so I replaced it with a new motorcraft one as every thing I have read and researched pointed to it. I also cleaned the throttle body and egr valve. so this isn't normal then? I figured it wasn't which is why it has been driving me nuts.

 

There are 3 sources of signals that are involved in up and down shifting points the computer arrives at to direct transmission shifting.
1. The IAC.
2. The Throttle Position Sensor.
3. VSS speed sensing.
Other than trying this and that, a Scanner looking at live data for these operations should show which one is the cause.
Some times you have to do more involved diagnostics when there are no codes to offer direction.
Good luck..

 

Thank you for the response. I will do some logging today on these sensors to hopefully start to figure this out. I have an sct and can log through that device. I will post up if I can track this down.
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