Scrid

Hi everyone, I was hoping someone could shed some light on an on going problem I seem to be having with my 98 E-350 service truck.
The truck started dying after starting it up about 9 months ago and the CEL was on.
If you hold the pedal down to increase the idle it will stay running but when you let it idle down it dies again.
I had the code pulled which was a P0505 indicating an idle air control problem. A vehicle tech friend who lived here at the time helped me with it and when we noticed the engine was actually acting up,... that if we rapped on the idle air control valve the engine would instantly idle on it's own.
I replaced the IAC valve and had the codes cleared.
The truck ran fine for about a month and then it started doing the same thing again once in a while. I lived with it since it was so intermittant, but then it became worse. Once again the CEL light was on and I had the same code P0505.
I replaced the IAC valve again thinking I might have had a bad one and the engine ran fine again for another 2 months. Now it's doing it again and it is getting more frequent. It will do it when the engine is cold or after it's hot. Sometimes if I gun the throttle it clears right up like nothing happened. Other times not. Sometimes I'm forced to keep a foot on the throttle with the idle up and one on the brake so I can keep it going while I put it in drive and get moving. When I slow to a stop the ignition light on the dash comes on indicating the engine has died and I lose my power brakes. it's getting really annoying and kinda dangerous. Any thoughts or help are appreciated.
Thanks.
Chris

kaboom10

Basically you need fuel, spark and air to run your engine. You're looking at one of 3 possible problems. What is the driveability like? Do you encounter any time a non-smooth throttle response? obtw check all the connections and wiring to your IAC motor as that is most suspect. Clean and inspect the connections closely for damage and/or dirt. You didn't wash the engine did you?

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02 F-150 FX4 w/Baer rotors,carbon kevlar pads,SS lines,remote coolers/filters. IAS shocks,LiveWire tuned by me.