Where is the iac valve on a 2003 f150 5.4l triton v8? my truck will idle steady but when shifted into drive or 1 the rpm drops and stalls engine also when coming to a stop it will act like its stalling just before coming to a stop then the rpm will jump back up to normal this will happen around 80% of the time i drive. Also when I get to 45mph the truck will shake fairly hard until i get to about 65mph and then its fine. Had some mechanic say it was my transmission going out from the torque conv. Beating against the drum? i know nothing about transmission problems but the fluid is nice and pink and doesnot smell burnt at all. 91000 miles on truck and trans. Has been serviced twice and overall been well maintained. If someone could give me an idea of what the problem is it'd help out a great deal thanks.
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I believe the idle is controlled by the idle air control valve (iac), not sure when they switched to it in the late 90's. Also, if its dying after startup up, check around throttle body for an (iac) and it will most likely be cylinder shaped and have one electrical connecter.
There is a mod for this problem. Insert a 1/2" copper pipe cap with a 1/4" hole drilled in the cap, into the rubber IAC pipe. This restriction helps fix high idle and thumping from IAC valve. Ford has a "muffler in line" fix for this issue, but for a $.50 copper cap, why give $50 to Ford engineers.
P1504 Idle Air Control Circuit Malfunction, take off the idle air control and inspect the inside. the pintle inside can get dirty and cause it to get stuck. try cleaning it out with some brake clean and see if it helps. dont spray it ont he electrical connection though.
Could be the IAC valve (idle air control) , a vacuum leak or several other things. Take it to a local autoparts store and have them read the codes in the computer. That should tell you more. Reading the codes is usually done free of charge.
The Idle air control valve (IAC) is on the back of the throttle body housing on the 4.6 V8, it's half the size of a can of Red Bull. Try tapping on it with a small hammer and if the truck clears up then it's time to replace the IAC.
You can clean it with Throttle body injector but that's just a quick fix for now. Good luck and hope this helps.
does it idle ok? Check your IAC valve.(idle air control valve) Start the engine and turn on the a/c. Does engine bog down? It should remain steady if not the IAC is bad.
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