Throttle sticking again

[shadow460]

When I got my Expedition, occasionally the engine would race when I had it in park or neutral. My scanner showed that the throttle position was varying between 18 and 22%. I cleaned out the throttle body as per advice given here and it settled to 18% consistently. The problem vanished... for a while.
Said problem would return every few months and I would clean the throttle body out. Now it's recurring no matter what I do.
I don't believe dirt or gunk has anything to do with it anymore. The problem showed up tonight. At idle the TPI was showing 19.6% throttle. The passenger door was open. My wife climbed into the passenger side and as soon as she did, the throttle position went up to 20.% and the engine began to race again. I shut the engine off and restarted. The throttle went back to 18%. I kept the scanner hooked up during our travels this evening and every time I let off the gas I got 18%.
The throttle linkage moves smooth. The throttle plate and throttle body are squeaky clean thanks to the in house O'Reilly throttle body cleaner, some rags, and a soft toothbrush.
I am completely at a loss here. The only things I can think of are the TPI itself and/or the spring that returns the throttle to a closed position.
Engine is the 4.6 Romeo with 4R70W tranny.

Any ideas?

 

[stamp11127]

The next time is sticks try pulling back on the gas pedal with your foot. If the idle drops back to normal the throttle body isn't closing all the way. It may be binding inside or the cables may have a rough spot to them. If there is a cruise control cable check that also for ease of movement.

If everything passes then the TPS is suspect. There is a procedure for checking the voltages throughout its travel which may show a spot that binds.

While your looking over the cables it wouldn't hurt to check the electrical connections in the plug for bent or corroded pins.

 

[Jonny42]

You should also look into the idle air control valve....unfortunately cleaning the throttle body does not remedy the problem if the IAC is dirty....you can remove it and clean it but be careful with the gasket....or you can purchase a new one with lifetime warranty for about $40 which includes the gasket

 

[shadow460]

I usually lift up on the gas pedal when the throttle sticks, but to no avail. I was messing with it yesterday and put my hands on the air intake. That caused the idle to surge again.
I think the cruise cable is damaged where it sits between the air intake and the upper radiator hose. There's always slack in the throttle cable when the pedal isn't being pushed. The cruise cable had only a little slack in it, if any at all. I flexed the metal plate that holds the cable to give it more slack and messed with the air intake again. The idle didn't change that time. It's possible I may have bent that plate at some point or it may have been bent in the previous owner's accident.
I have considered if the idle air motor is causing this, but the throttle position shown on my scanner doesn't seem to take the IAC into account. If I do anything to it, I'm going to drop the cash on a lifetime warrantied one, though, just for the peace of mind.
Thanks for the replies, though. Keep 'em coming!