IAC replaced, fixed surging idle and code p0123
many thanks to all the people on this site for posting their knowledge, otherwise i never would have known how to fix this.
my truck has been acting up for a couple of weeks, surging at idle. like someone was mashing the gas. it started doing it only when cold, but has gotten worse, and today it started dying at idle and threw a code p0123 (tps voltage too high) which is misleading. (i had already changed the tps about 6 weeks ago and that solved some surging on cruise problems). so i picked up a IAC at local auto parts for about $45 and changed it today. some people had mentioned cleaning it but for $45 why bother. i was able to reuse the old tb gasket successfully.
it was fairly easy. the hardest part is standing on a short ladder and then kneeling on the front bumper and trying not to fall over onto the motor. remove air cleaner. disconnect 3 sensor wiring connectors from throttle body. tps on drivers side, iac in rear and something in front (map maybe ?). to get the connectors loose i put a flat screw driver between the end of the plug and the tb and twisted the blade gently to put a little pulling pressure on the connector and squeezed on the tab. they popped right off. on the passenger side there is a flat black bracket holding three cables, 2 coming from front and 1 from rear. remove the two cables on the outside by pushing away from the direction of the cable and they just pop off. i couldn't reach the inside one yet. remove the 3 bolts that hold this bracket to the tb and just let it drop off the side of the tb. bolts are small, maybe 10mm or less. next remove the 4 bolts that hold the tb on. 13mm. this is all aluminum, so be gentle, i loosened them in a cross pattern a little at a time. lift the tb and turn it over and remove the 3rd throttle cable. take care not to mess up tb gasket or drop anything into intake. take tb over to the bench. go back and look down in plenum and see.... lots of oily reside. hhmm...(plenum gasket) big job for some other time.
cover plenum so nothing falls down in it and go back to workbench. remove all 3 sensors with torx #25, keep bolts id'd. be careful with little hose on front sensor. my iac was all gunked up. remove o-ring from old iac and place onto new iac !! spray tb all over with spray can of carb cleaner, scrub all over with toothbrush and finger, expecially clean iac well including 2 or 3 little tubes, the plates, the big holes the plate pivot in, etc. wipe clean. reinstall new iac (dont forget oring). iac should fit in the well without contact to the end. if you have contact, stop and check directions on iac to twist it in to compress it. install tps, front sensor (dont forget the little hose).
reinstall in reverse - inner cable, bolt tb on, black cable bracket, 2 outer cables, 3 electrical connectors. i messed up on the outer front cable, it routes under the black v shaped piece, not over. check that gas pedal opens tb, my cable was wrong and it wouldn't open up. clear codes if possible, crank it up. mine whistled like crazy and idled high for about 30 seconds while it set the iac position, then it ran normal. reinstall air cleaner. test drive. admire your work.