How to: Diagnosing Rough Idle - Suspect: IAC Valve

[ExplorerDMB]

If you are expierencing a rough idle and you have a feeling it is the IAC Valve - Use a hammer and LIGHTLY tap the motor to see if there is a change in idle or the vehicle starts to idle correctly. Some IAC Valves will give a hiss/noise at idle. If you unplug the IAC and the noise goes away - this is your issue. Also, if you unplug the IAC and the idle is a little high, but better - then your IAC is probably bad.

This is a IAC Valve and it's location on a 4.0L SOHC Ford Explorer

-Drew

Visit here to read Karl Burns write up on IAC Cleaning

 

[dogfriend]

If you tap really hard with the hammer you can definately affect the idle, but you will probably need to get another IAC valve.

 

[myrockfight]

Don't replace yet - try cleaning first.

I have cleaned my IAC twice now at 130,000 miles. I just unbolt it and spray it with ether to clean it up. Last time I used some q-tips to help get the carbon residue out.

It runs perfectly now! So give the cleaning a shot before you go and spend your money needlessly.

 

[BrooklynBay]

Here are 2 threads written by Glacier991 on the IAC:
http://www.explorerforum.com/forums/showthread.php?t=154705
http://www.explorerforum.com/forums/showthread.php?t=120221

 

[BrooklynBay]

Here's an article on cleaning the IAC on a 5.0 Mustang: http://www.moddedmustangs.com/cleaning-your-iac.html

 

[ishmelvampire]

it could also

hey it could also be the throttle plate is really nasty and the area around it. clean it with cci air intake cleaner and a rag. carbon builds up there and when it gets really bad it clogs. and the iac valve has to work really hard to compensate. it could get so bad that the air cant get in at idle. seriously

 

[pirinola]

please help !!

I have changed the IAC brand new one the iddle problem went away completely for a while but now after a few weeks the revolutions in the truck does not stay where they need to be I have to keep my foot in the gas or the truck goes off , when I changed from od to od off the truck stabilizes a bit better after warm up the engine the truck in od responds good , please any help in this case will be appreciated .....details sohc 5.0 2000 explorer .
Thank you in advanced.

 

[BrooklynBay]

Do you have a check engine light? It could be related to another part, like the MAF sensor for example.

 

[bikerted86]

Ive had issues with cleaning the iacs on the ohc motors, once in a while youll clean them and then they will create a loud houling noise. Also with the plastic intakes it is very common to have vacum leaks around the gaskets which will cause a missfire or bad idle. Try spraying carb clean around the gasket and injector area with the engine idling and watch for a sudden change in idle. If there is a change then theres a leak.

 

[dogfriend]

Ive had issues with cleaning the iacs on the ohc motors, once in a while youll clean them and then they will create a loud houling noise. .

You mean like this??

Wooooo!

:

 

[bikerted86]

that would be it, Yeah heard that way too many times.

 

[dogfriend]

I heard that noise once in a parking lot from behind and immediately thought that it was an Explorer. I was wrong. It was a Ford Contour.

 

[BrooklynBay]

The Ford P/S pumps have a very distinctive sound to them. You could tell it's Ford when you hear one!

 

[Adam96ltd]

you could also have a clogged egr system. the egr is only active at low and idle rpms, and it uses vacuum to oull in used exhaust gases. if there is a block in the system it would lead to a loss of air and possibly a rich condition.

 

[J. Anthony]

No start, rough idle...

Would this keep the motor from starting? My motor turns over but will not fire. Sometimes it starts but idles extremely rough and the smell is as if the fuel is not burning. Crazy, but it seems to happen when it is humid or rains the night before. Could this be the issue?

Anthony

 

[dogfriend]

. Crazy, but it seems to happen when it is humid or rains the night before. Could this be the issue?

Anthony

Check your ignition (plug) wires. The increased humidity can cause misfiring if the insulation is old and cracked.

IAC could possibly be an issue, but usually the truck will start but the idle speed will be too low.

 

[J. Anthony]

This morning I opened the hood and just stared down by the plug wires hoping to see some arc'ing; nothing. I plan on changing the plugs and wires when the rain stops. I did notice that there are a lot of issues with the MAF. I have changed the MAF about 50,000 miles ago. I took it off and cleaned it but it didn't help. Finally, out of nothing else to test; I had a real machanic check for codes with a diagnostic but there were no codes to be got; anyway, I took the air intake off and right at the throttle body I sprayed some starter fluid...BAMM! It started right up. Idle was real rough but it was on. I drove about 5 miles with absolutely no power. But it cleared up the CEL went off and it's like it never happened. What do you think? I have been trying to diagnose this for months now.

Anthony

 

[dogfriend]

You could try cleaning the IAC, but my gut feeling is that you have an ignition problem. I would change the plugs and wires and then go from there.

 

[J. Anthony]

You may have something there...

A mechanic thinks I may have a bad plug or a bad wire. I was hoping you would say such. I think tommorrow when I get back from the Farm I'll do the change. What makes me think you are right is that I started running rich in the past few months, that was a big change in the engine. Any plugs you would recommend? I have been using Autolite. They have always seemed to perform well. I get most of my parts from NAPA. Should I try to get some better wires from Summit or JEGS?

Like the pic's of your pets. I have five. I am a TBAR Volunteer here in Washington County, Texas. Love the dogs. I have taken out the back seats, carpet, and made a rubberized back for the dogs. I even take my dogs to work with me; I work for Banfield Pet Hospital.

Anthony

 

[dogfriend]

The Motorcraft Double Platinum (OEM) plugs are actually pretty good. I also use Motorcraft wires, but there are several good aftermarket ones too. I think the original wires are 8mm silicone, so I would try to get that quality or better.