Today I seafoamed the truck, new plugs wires, screamin demon coil pack and oil change. So I decided to clean the IAC and throttle, came out real nice...BUT now everything is back on it started idling at 2k, I swapped another IAC in, it dropped to 1500 rpm then to 1000rpm My truck as always idled at 500-600 rpm. There is a sensor that goes on the side of the throttle here on the side



I put the sensor on, it has to be put up on an upward angle like this


Then pushed down to line the screw holes up like this, and by doing that, it turns the cylinder a bit once its lined up


When I start my truck it is steady at 1k at idle, I give it gas it races to 2k rpm then after a minute drops to 1k. I loosen the screw to that sensor, when it moves the idle jumps. Am I messing up here or what?
I took it out for a drive real quick. In park it idles at 900 rpm, in gear idles at 800 rpm. When in park if I rev it once and let off, the idle will drop to 1500rpm for a few seconds then it will drop to 900 rpm. So WTF is going on? Anyone??

 

I just cleaned the IAC and MAF on my 4.0 SOHC and noticed the same thing. It cleared after a day or so of driving and is now back to normal. Not sure what caused it, but it's fine now. What did you use to clean the IAC?

 

I used a throttle and carb cleaner, I know it was made for stuff like that. I just dont get it

 

Im not sure but i think that may be your problem. The iac may now be bad. You have to watch what you clean the intake parts with, i cleaned my maf sensor with intake cleaner, big mistake, and i had to buy a new maf.

 

Yeah I used what was recommended, I didnt clean the maf, only the throttle body and AIC...so I will buy one and see if that does it

 

I was told to use electric contact cleaner on the IAC. Maybe that's your issue?

 

I am starting to think the original owner had the throttle adjuster screw cranked in a little bit. I turned it out some and the idle did drop.

 

Speaking of the idle setting, what is normal for the 4.0L SOHC?

 

Mine has always idled at 500-600 rpm

 

I have been doing my homework and checking my chilton book which I should have done in the first place. By turning the screw out, it still seemed like it still wasnt running right, I used almost 1/2 tank of gas in 42 miles which wasn't good. It seemed not to be the same so I finally soved the problem. The dumb *** I am followed the "How to" But failed to realize some throttle cleaners have solvents. I used this throttle cleaner on both of my IAC's and both throttle bodies. Throttle bodies turned out great, the IAC looked great as well. Turns out the solvent ruined both IAC's, thats why swapping them didnt help because I ruined both. Tonight I turned the screw back to its normal position, and put on a brand new IAC and the Hooligan runs beutiful!!

So word to the wise when cleaning your IAC.... DO NOT USE A SOLVENT!!

 

Cleaned the IAC last week because my truck was stalling when I shifted into park. That problem seems to be gone, but now in the past couple of days I'm also noticing it idling a little higher than normal (around 1000rpm). No significant change in fuel mileage as the OP mentioned. Should I look further into this, or is it better left alone if the engine is running fine?

 

What size engine do you have and what did it idle at prior to cleaning the IAC?

 

use Mass Air Flow sensor cleaner it MADE for IAC and MAF. for cleaning the throttle body i used FoMoCo TB cleaner

 

4.0L SOHC. Used to idle around 6-700rpm it has been up around 1000rpm.

Update: Cleaned it again and it's running normally again. Perhaps the IAC is going to need to be replaced soon.

 

Yep solvent based cleaners on electronics do not mix.

 

Did you remember to adjust the TPS output voltage when you reinstalled it? have to use a multimeter to do so, other wise it will trip a code and will run like crap. I think the output should be between .95 and .97 volts. usually your computer will adjust your idle accordingly UNLESS it is to far out to begin with.

 

Now I notice you guys say idle in this post but what do you mean idle? idle when it is in park/nuetral or in gear. My truck sits at 1000 rpms when in gear but drops down to 500-600 rpms when it is in park or nuetral.... is that normal. I changed the Idle Air Control (IAC) Valve because the truck would die in park, but not everytime. when i changed the Idle Air Control (IAC) Valve and i shift from drive to park it goes from 1000 rpm to 500 rpm but doesn't die anymore.

 

Here's an article concerning the IAC valve. I too am having problems with my IAC valve causing a humming noise in the air intake. I cleaned it with carburetor cleaner and set to let dry. It actually made it worse for me. The humming stopped, but the truck stopped idling high enough to prevent stalling.

This article is from Ford and you can take their word for it to just buy a new IAC, but they only see it as a short lived solution.

Note: This is for a Crown Vitoria, but the application is the same. Here's the link to the article.

http://p71interceptor.com/repairs/iac/