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I have a 1993 ford f-150 351 4x4 auto. The idle is too high 1600 rpm and the transmission is shifting hard 1-2 2-3. I looked for a vacuum leak and did not find one. It also failed the wash emmision idle test. What could be the problem?
could possibly be the idle air controller. its a cylinder about 4 inches by 1.5 inches on the side of your throttle plugged in and held in place with 2 bolts.
could also be the throttle position sensor on the bottom of the throttle held in with two cross tip screws. (i dont think it will come off without removing the throttle)
might be something completely different
i had the same problem but my idle was at like 2500. it wouldnt start without a shot of ether. replaced the tps and it started right up and idled smooth at 800 rpm.
A high idle can be caused by vacuum leaks, a faulty TPS, sticky IAC or a previous owner jacking the idle stop screw. Because you also have a transmission shifting problem as well I would suspect a problem with the Throttle Position Sensor (TPS). But as I noted before check for codes first.