Idle Air Controller

On Wed, 07 Apr 2004 20:45:37 +0000, Bryant rearranged some electrons to form:

It's near the throttle body.

What makes you think it needs to be replaced?

I have had a situation that happens about a half dozen times a year and a mechanic suggested that it was my idle air controller going bad..

This is how it usually happens: I'll take my truck out and go driving around and then stop somewhere and go inside. I'll come back and start my truck. It fires right up but the moment I take my foot off the pedal it dies. I'll start it up again and it dies again. The engine will continue to run as long as I keep my foot on the gas pedal but the moment I remove my foot, the engine will die. I will usually wait about fifteen or twenty minutes and try again and the problem will go away --- the truck will then idle in park and not die when I remove my foot from the gas pedal. I am then able to drive away with no problems.

Also, my truck has never died while I am waiting at a stop with the transmission in drive and my foot on the brake...This problem only happens when I am in park.

If you think there might be another problem I would appreciate any suggestions.

||I have a 1994 Ford-150 with a 302 engine. I would like to know where the ||idle air controller is located and if it can be easily replaced or if it ||should be left to an experienced mechanic.

You can get to it easily and remove it with common hand tools. First step is to buy aHaynes manual or find a website with instructions. Rex in Fort Worth

That sounds exactly like the IAC. The way the system works is : .) push the pedal, open the throttle, air flows in the engine .) let go of the pedal, close the throttle, air does not flow to the engine, the engine stalls in this scenario, the computer is supposed to tell the IAC to open a certain amount. The IAC valve is an alternate route (not through the throttle plate) for air to enter the engine.

As a result, if the IAC sticks closed, the engine will stall unless you hold the throttle open.

A simple solution is to disconnect the intake hose from the throttle and spray some Intake Cleaner in the throttle body while the engine is running (and the throttle plate is closed). Naturally the engine will start to stall, so push the throttle open (rev the engine) to compensate. Alternatively, take the IAC off and use the same Intake Cleaner with the valve not connected to the engine. This worked for me on my BroncoII.

-D

Assuming your throttle body is not gummed up, that does not sound like an idle air control. The problem may be corrected at the same time a tech replaces the IAC but, this would likely be a result of him cleaning the throttle body. If the throttle body is reasonable clean, a bad IAC will usually result in an erratic idle, incorrect idle speed or low idle speed but, not a complete stall that clears after sitting if the base idle is correct. You should have a diagnostic scan done for stored fault codes before replacing any parts; they can get very expensive without fixing the problem. You should also take steps to ensure that the engine is in a good state of basic tune before throwing parts at it. This would include the condition of the plugs, wires, cap, rotor, filters, etc. That does not mean to go out and buy all of this at one shot unless it has been a long enough interval that it should need it anyway.

Lastly, since your problem only occurs in Park, it may be related to the MLPS or nuetral safety switch or whatever it is called on your particular year truck. It is installed on the transmission and tells the computer what position you have selected. The ECM uses that info to control several functions of the engine and powertrain. The fact that you seem to have a proper idle when in any position other than park suggests this may be involved. It is not a particularly expensive sensor nor, is it difficult for an intermediate or lesser level DIY'er to replaced with basic tools. Like any other part in the system, it's replacement may or may not correct your problem in the absense of a diagnostic scan by a competent technician to see exactly what is going on.

Lugnut

Thanks Derrick 'dman' and lugnut.....

I have had about twelve cars in my life but my 1994 Ford F-150 was my first brand new automobile. I miss the days when I could lift the hood of my car and see only a carburetor, engine and transmission! There was so much stuff under the hood of my truck that from day one I decided to have a mechanic do most of the work that I didn't think I could handle.

I am going to attempt to replace the IAC and clean up the throttle body and see if the problem happens again.

Thanks for the help...

On Fri, 09 Apr 2004 10:25:58 -0400, lugnut wrote: [...]

Not a bad idea. Regarding the EEC-IV (at least that's what my '93 has) see these sites :

can do the test yourself without a scanner. OTOH the scannercosts ~$30.

(note: Autozone and Adv. Auto Parts scan codes for free, but they only use OBD-II scanner and thus can't scan your vehicles older than 1996)

I didn't think of this, but then again I favor manuals and thus don't have this part :-).

-D

||(note: Autozone and Adv. Auto Parts scan codes for free, but they only ||use OBD-II scanner and thus can't scan your vehicles older than 1996)

I don't think that is true for AZ. they have a pretty expensive scanner that does OBD 1 & 2, and I'll just bet they can do the earlier ones too, since that's pretty simple stuff.

Rex in Fort Worth

See the idle air controller solution listed at

It will only cost about $2 for a can of cleaner and 20 minutes of your time to determine if this is your problem.

Assuming your throttle body is not gummed up, that does not sound like an idle air control. The problem may be corrected at the same time a tech replaces the IAC but, this would likely be a result of him cleaning the throttle body. If the throttle body is reasonable clean, a bad IAC will usually result in an erratic idle, incorrect idle speed or low idle speed but, not a complete stall that clears after sitting if the base idle is correct. You should have a diagnostic scan done for stored fault codes before replacing any parts; they can get very expensive without fixing the problem. You should also take steps to ensure that the engine is in a good state of basic tune before throwing parts at it. This would include the condition of the plugs, wires, cap, rotor, filters, etc. That does not mean to go out and buy all of this at one shot unless it has been a long enough interval that it should need it anyway.

Lastly, since your problem only occurs in Park, it may be related to the MLPS or nuetral safety switch or whatever it is called on your particular year truck. It is installed on the transmission and tells the computer what position you have selected. The ECM uses that info to control several functions of the engine and powertrain. The fact that you seem to have a proper idle when in any position other than park suggests this may be involved. It is not a particularly expensive sensor nor, is it difficult for an intermediate or lesser level DIY'er to replaced with basic tools. Like any other part in the system, it's replacement may or may not correct your problem in the absense of a diagnostic scan by a competent technician to see exactly what is going on.

Lugnut