Fast Idle, help!

[galbre]

All,
I noticed recently that my Explorer started downshifting roughly from 3rd to 2nd and 2nd to 1st. My truck has 130kmiles so I was initially worried that my trans was on the way out. Upshifts are fine though.

I also noticed that when I start it up that the idle is real fast at about 2100 rpms. When I shift it into drive the RPMs drop to about 1100rpms. Even 1100rpms is abnormally high. It usually idles at around 700rpms. Now at 1100rpms if I let off the gas it will pull away without me even touching the gas. If i put the truck into neutral the rpms will increase to 2100. Once I put it into drive the rpms drop to 1100.

I'm wondering if the rough downshifts and the fast idle are related? It might make sense that as the trans goes to downshift the RPMS are too high causing a rough downshift.

Any suggestions on how to fix this fast idle? Last month I cleaned the MAF, replaced the air filter, cleaned the throttle body and the EGR valve.
Thanks in advance.
Gregg

 

[Javadog123]

Clean your idle air control valve and check for vacuum leaks.

 

[matt0248]

Replace the IAC valve, cleaning it may not work. My 02 V8 was doing a similar thing. I replaced it with an atuozone one after trying to clean the original one. The replacing it fixed the high idle but i never lilke how the idle will roll a lilttle with the AZ one. So, i eventually bought a motorcraft one of Amazon for $45 bucks or so, i got lucky and found a cheap one. no problems since.

 

[galbre]

New iac from Ford is $153. I'm going to try cleaning it first. If that doesn't work I'll replace it. Any suggestions on what to use to clean it? Thanks.

 

[matt0248]

Motorcraft ones are $70 something on RockAuto.com and you can get 5% off with a discount code for being a forum member. As far as cleaning goes, you can use throttle body cleaner or carb cleaner. The problem is you only clean the pintle and seat. You cannot clean the electical coil which drives the pintle. This is usually what goes bad so cleaning it may not work.

 

[esclamada]

I'll try cleaning first instead of buying..

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[galbre]

All,
Thanks for all the help and suggestions. I decided to replace the IAC and get the part locally so I could change it this weekend. I wound up calling around and was surprised on the range of prices from Ford dealers. Most were $138 but some were as high as $153 for the IAC valve. I finally found one that sold it for $99. It is unbelievable that some dealers mark the price up that much.

Put it in today and it only took 20 minutes taking my time and even cleaning the port on the throttle body.

It solved my idle problems completely. Thanks for all the help and suggestions. I havent driven it enough to see if my downshifting has improved but the dealer felt that was unrelated and most likely a transmission solenoid issue, hopefully not.

Gregg

 

[matt0248]

All,
Thanks for all the help and suggestions. I decided to replace the IAC and get the part locally so I could change it this weekend. I wound up calling around and was surprised on the range of prices from Ford dealers. Most were $138 but some were as high as $153 for the IAC valve. I finally found one that sold it for $99. It is unbelievable that some dealers mark the price up that much.

Put it in today and it only took 20 minutes taking my time and even cleaning the port on the throttle body.

It solved my idle problems completely. Thanks for all the help and suggestions. I havent driven it enough to see if my downshifting has improved but the dealer felt that was unrelated and most likely a transmission solenoid issue, hopefully not.

Gregg

glad you got it fixed. whoever at the dealer told you that it was unrelated is an idiot, probably a prts person who has no clue. It aboslutely had something to do with the harsh downshifting. transmissions downshift really bad when the engine rpms are really high.

 

[galbre]

Well, its a couple weeks later and the fast idle is back

Just to recap, I replaced the IAC valve with a new one from Ford. Does anyone have any ideas on what else to check?
Thanks,
Gregg

 

[matt0248]

If you unplug the IAC when the high idle is happening does the truck stall? Have you cleaned the throttle body? Maybe it is sticking. It is also not out of the realm of possibilities that the new one took a dump. you could try getting it replaced, i assume if it's only been a few weeks the part should still be warrantied. I guess it could also be a PCM issue of not sending the right control signal to the IAC.

 

[bel4_20]

Well, its a couple weeks later and the fast idle is back

Just to recap, I replaced the IAC valve with a new one from Ford. Does anyone have any ideas on what else to check?
Thanks,
Gregg

Hi i have the exact same problem as you(rough shift and all) i remedy it buy disconnecting the battery for half hour clears the problem for a month to ?... but it does come back. I was about to replace the IAC but i see this is not the issue I suggest you start looking at the TPS, at least thats where im looking next. Next time this does this to you go ahead disonnect the battery for 1/2 hour and ill put money that will temp fix the fast idle(not that it's a fix). Any other input would be great on this.

Thanks

 

[galbre]

I tried a brand new TPS and that didn't fix it. I did notice that the throttle body seemed slightly stuck open when no pedal is applied. I'm going to take it off and clean it this weekend.

 

[Shame]

Yup... I have the EXACT same problem as well. I replaced my IAC with the one from Ford just last week and now Ive got a high idle and nasty downshift issues. Have you looked into the possibility of a vaccum leak? I think thats what Im going to try next. Ill let you know how I make out.

 

[matt0248]

Yup... I have the EXACT same problem as well. I replaced my IAC with the one from Ford just last week and now Ive got a high idle and nasty downshift issues. Have you looked into the possibility of a vaccum leak? I think thats what Im going to try next. Ill let you know how I make out.

Did you disconnect the battery after replacing the IAC? The computer needs to relearn idle speed with the new one. Also, clean your throttle body. Carbon build up can sometimes wedge it open slightly.

 

[Tom N]

I have this same issue. High idle with hard down shift. It only downshifts hard when its idling high. When its idling normal it downshifts normal. I do not have any vacuum leaks as I checked. I have cleaned the throttle body in case something was sticking but I dont believe it is. I also can make it go away for awhile by disconnecting the battery. Sometimes it will start doing it again in a few days some times several weeks. I dont think disconnecting the battery would do anything if it was a sticking throttle body or a vacuum leak. I also dont have a check engine light on. Simply cant figure out what causes this. Very annoying.

 

[underdog1799]

I have this same issue, although I have replaced my IAC with one from Autozone. I'm not sure what is going on with it because when I shift to neutral when the idle is high it will rev up to about 2100 RPM and then after 3 seconds drop to 600 RPM. Occasionally when i'm in drive it will go down to 600 RPM when i'm not pressing on the gas pedal, but most of the time it is at about 1200 RPM. Anyone find any solutions to this issue?

 

[matt0248]

Get rid of the AutoZone IAC. I have tried AZ's and Borg Warners from Advance and neither worked as well as the Motorcraft ones.

 

[underdog1799]

So you think it is the AZ IAC that is causing the issue? Where can I get a Motorcraft IAC for cheaper that $134? (OreillyAuto)

 

[matt0248]

So you think it is the AZ IAC that is causing the issue? Where can I get a Motorcraft IAC for cheaper that $134? (OreillyAuto)

rockauto.com plus there is a 5% discount for bieng a forum member.

 

[underdog1799]

How do I get the 5% discount?