New IAC, still setting high idle code

[fullmonte44]

Help please. Have 2002 Exp. with 4.6L, keep getting code 1506. Ford dealer replaced IAC when doing other repair of rear main seal leak. At startup still seems idle is too high. As it warms up, some decrease, sort of settles when warm at just over 1,000 rpm (like 1050, perhaps). Erase code and it comes back in couple of days.
I have checked the PCV valve and operation. That seems okay, good valve and there is vacuum on the hose. I know it could be an air or vacuum leak, but I've been looking-all hoses seem intact. I put a vacuum gauge on it- I got a steady 16-16.5 inches. That may sound low to you, but I am at 4500 feet altitude, and I have yet to find a vacuum reading on other engines here that is over 17 inches-really it seems like 16 here is right at the normal. Anyway, no whistling sounds. You think I should spray carb cleaner around the intake to check for leaks? With all the stuff on top, is it even feasible?
Any help is appreciated. My son mentioned another code he found one day, but erased them all, and cannot recall what it was (!), he thought it might have been related to EGR system. That was about 10 days ago. Since then, the only code showing up over and over is 1506- high idle detected. Any suggestions? Beyond possible vacuum leak I mean, which I plan to keep looking for. Arrggh, Help!~

 

[imp]

@fullmonte44
Try disconnecting the vacuum hose from the Power Brake Booster and plugging it with a cork. If engine idle slows down, ya got a leaky booster diaphragm. If that ain't it, yes, carb. cleaner is recommended as a means of detecting vacuum leaks, seeking idle speed change from the added "fuel". Throttle Body next: IAC gasket missing or broken; IAC stuck partly open, take it off and see if the plunger inside can be moved easily against it's spring-load. A skinny pen-knife will usually work. No luck there, Throttle Body gasket check. Hope one idea connects for you. imp

 

[fullmonte44]

Okay, thanks, Imp, will do as you suggested. But one of the places I hooked up my vacuum gauge was on the brake booster hose, and that did not affect idle at all, so I know the booster is not the problem. So throttle body gasket, IAC gasket, Intake is next, it looks like. This is a ford dealer replaced IAC valve, only a month or 6 weeks ago. but If nothing else turns up, I will pull it off and check it, as suggested. I could rant forever about dealerships, but it's a pretty well-known story, so will just grin and bear it. I really don't know if they noticed the high idle, but $1875 in labor costs for the rear main seal means I won't encourage my son to take it back anytime soon. When they got done with him, his final bill was $2500. I've told him many times before, this time I didn't utter a word. He is catching on fast enough.
I see you are from the Ozarks, what city or town? I grew up in NW Arkansas, just south of Fayetteville, AR. Been here in Montana for the last 40 years, 44 years to be exact. Came here in 1972 with the VISTA program, kind of settled in over the years. Cheers and thanks.

 

[lincolnshibuya]

why you didn't bring it back to the dealer instead of figuring it out yourself? it could be a faulty IAC in the first place.

 

[imp]

@fullmonte44 ...."but $1875 in labor costs for the rear main seal means I won't encourage my son to take it back anytime soon. When they got done with him, his final bill was $2500. I've told him many times before, this time I didn't utter a word. He is catching on fast enough." This is why we band together to try to figure out, second-guess if necessary, and otherwise side-track the astronomical (and ridiculous) price of having dealership repairs performed.

"I see you are from the Ozarks, what city or town? I grew up in NW Arkansas, just south of Fayetteville, AR. Been here in Montana for the last 40 years, 44 years to be exact. Came here in 1972 with the VISTA program, kind of settled in over the years. Cheers and thanks. Actually, we lived in the Ozarks from '99 till 2012, when we moved to west-central Arizona, along the Colorado River. Had 1/3 of a 300 acre piece of forested ground bought in a threesome with my nephew and a neighbor from the Phoenix area, where we spent the 20 years previous to '99, near the little town of Bunker, MO. Considered Pocahontas (AR) as a possible settling place, nice river there, but decided the area looked like it was dying. Ever hear of Roundup, Montana? Looked at a possible retirement there in the '90s, decided too cold. FWIW, my nephew served with Vista in the Dallas area as a young man, around 1972 also. imp