My <B>SOHC 4.0 Stall Symptoms:</B>
Stuck on the second tier of a multi level parking lot at 8:30 one rainy Poughkeepsie NY October evening-
My wife and I were confronted by the way our Explorer would start for a moment but quickly stall out after the gas peddle was released to idle-

After repeated attempts to keep it going- I discovered that the only way to get the car home without the need for tow, would be to drive w/one foot on the gas and the other riding the break- while never releasing the gas at idle.

This is dangerous and though I would not highly advise it – Well it worked for us- and only stalled out once – Later - After much re-searching these Net sites and a hard to read ford shop manual I have on CD - I was able to repair and photograph what turned out to be my defective----

<B>IAC Valve</B>

First
Remove four hex screws holding the plastic cover

Check the cable harness carrying voltage to your IAC-

Disconnect lAC valve,

Key on, engine off.
Measure Voltage PWR circuit voltage at the lAC valve harness connector.

Test Connectors supply of power to your IAC


Is voltage greater than 10,5 volts?
Yes;
KEY OFF, GO to KE3 (My valve measured 11.2 volts)

No;
REPAIR open circuit.

(My hope is that this is not your problem……As repair of an open circuit may be more difficult to trouble shoot than the
IAC alone)










************************************************** **********
<B>KE3 CHECK lAC VALVE RESISTANCE</B>

lAC valve disconnected,
Measure lAC valve resistance between the two pins,


Is resistance between 6.0 and 13.0 ohms?
Yes
GO to KE4
No
REPLACE lAC valve,

(Mine measured 0.022 therefore was very suspect at this point)



******************************************

<B>KE4 CHECK lAC VALVE FOR AN INTERNAL
SHORT TO lAC CASE</B>
Measure the resistance from either lAC valve pin to lAC valve case,

Is resistance greater than 10,000 ohms?
Yes

GOto KE5

No
REPLACE. lAC valve,

(With this my valve measured OL and therefore it became clear that a repair cleaning was of little use )












<i><B>Anyway - Further checks go on as follows if yours passes the above tests </B></i>
<B>KE5 CHECK AIR INLET FOR PLUGGING</B>

Inspect the entire intake air system for debris, blockage and other damage.

Remove and inspect lAC air tubes (if equipped) for blockage and other
damage.

Remove and inspect the air cleaner element for excessive dirt.

Is the intake air system OK?
Yes
RESTORE inlet air system. GO to


















<B>KE6 CHECK FOR INLET AIR LEAKS</B>
Key on, engine running.

With engine running at idle, listen for vacuum leaks.

Inspect the entire intake air system from the mass air flow (MAF) sensor
to the intake manifold for leaks such as:
Cracked or punctured intake air tube.
Damaged or loose lAC air tubes.
Loose intake air tube at air cleaner housing or throttle body.


lAC valve or gasket seal.
EGR valve gasket seal.
Vacuum supply connector and hose.













Many on the net have written about cleaning the IAC then re-installiung it- Well I think that is fine but- Only when it passes the electrical tests above – and cleaning also carries the added cash savings of about $65 or, in my case $88.00 dealer cost- I have only two warnings about it though and that is this;-

There may be a chance that while cleaning your untested valve, you perhaps may just rattle an intermitant internal short connection enough to make it work for a week or two – then when you least expect it- got ya!

This is why it is a good idea to electrically test first- Before that solvent, carbon q-tip cleaning I’ve often read about.

<B><i> Using these repair sites for many years I’ve saved some good bucks –Since I’ve been thankful but never said or written my thanks….. Well now I hope this helps someone out there! </B></i> And……. anyone out there who is thinking of sending flowers to a loved one in the New York Dutchess County Poughkeepsie area----Feel free to check out my Wife’s florist website……. Here is the link; http://www.afgflorist.com.

Until later………
Let those good Explorer times roll-

Chas Youngs
Poughkeepsie NY

 

Wolfmeister.... Excellent post!!!

Mike

 

Excellent post Wolf! And welcome to FTE!!! -:wink

I am going to sticky this to the top - I think this could help a lot of people!

 

Wolfmeister, that's a good tip about first checking the resistance across the IAC terminals.

A good clue is whether the vehicle fails to idle all at once. Since yours failed completely at start-up, an electrical problem is suspected.
If the idle slowly deteriorates over time, then the valve is probably getting a carbon buildup, and a cleaning will help.

Welcome, good first post!

 

Just one thought here... you said...

KE4 CHECK lAC VALVE FOR AN INTERNAL
SHORT TO lAC CASE
Measure the resistance from either lAC valve pin to lAC valve case, Is resistance greater than 10,000 ohms? Yes GOto KE5 No REPLACE. lAC valve, (With this my valve measured OL and therefore it became clear that a repair cleaning was of little use )

I think OL says that there is no connection between contacts and case... Which indicates it passed this test... however it failed the previous test so it's still no good.

 

Aletheuo- Yes you are correct in your observation-----
OL sure does represent the ultimate resistance and that does exceed the "greater than" > 10 k". Thanks! I was looking for a reading of some sort-

 

Hey, I believe I'm having this same problem. Whenever my Explorer is idling or at a low RPM(less than a 1000), it will struggle to hold idle and then die. I'm going to use your process to check what's going on with mine when I get home(at work now). My one question though is do I check resistance with the key on? I am 99.9% sure you check it without the key or engine on because it will ruin your meter if you check it with voltage going through, but I didn't know if you knew something I don't. But you may wanna specify in your article so those of us who aren't electronically inclined may still be able to do this check. Great article man.

 

Disconnect it and check resistances that way. Yes, key off.

 

Nice post! This is very easy to do.

 

I bought my IAC from NAPA here in Crystal Lake, IL for $59, had to order it though....My 98 everyonce in a while dies at idle...it has done it twice so figured iwould just replace it and be done with it...part come in a couple days....

 

This table might also be a help for those looking for IAC compatibility on many vehicles.
http://www.tomco-inc.com/Catalog/28...ss%20valves.pdf

They also have a product called an IAC spacer plate http://www.tomco-inc.com/Catalog/29...cer%20plate.pdf claiming to eliminate carbon-build up in the IAC and therefore lengthen it's life. This problem is bad particularly in '95 and '96 where the IAC valve is known to stick (Ranger and Explorer, Aerostar + many others). see TSB posted here: https://www.ford-trucks.com/forums/s...hreadid=164522

 

Found this site while searching for a cure to my 98 explorer's intermittent starting/idle problem.
Wolfmeister's experience in the parking lot experience identifies my problem as well. It has happened about 3 times in the past year. The first time it happened I couldn't get it running until I played with the gas pedal, then experienced the stalling unless I kept my foot on the pedal maintaining 1000 rpm or so. Also driving with feet on the gas and brake. After getting it started and driving it for about 150 miles on the interstate, and filling up with fresh gas, it ran fine. I figured I may have had some moisture or dirt in the fuel system. Anyway, things were fine until recently, when the same thing happened again. So, I drove it around and still wouldn't maintain an idle or start without working the gas pedal. The next morning it started fine. The first instance and the last, I know the temperature was below 45 degrees, I'm not sure if that has any bearing or is just a coinsidence since it wouldn't start or maintain idle even after reaching normal operating temp.
I think I'm answering my own question, but I suppose I could look at the IAC and try to clean, or replace it. This thing is an intermittent problem and when it's working, everything works fine. No other symptoms (when working normally), no rough idle, no hesitation (at any speed), no smoke, gas mileage is still 20+ and there is 85,000 miles on it. Regular maintenance per the maint. book. I've searched on this problem, and also noted some threads mentioning fuel pump problems. I make it a habit to listen for the fuel pump, when turning the key on... from experience with an F-150 with a bad fuel pump relay.
So, with all this in mind, is the IAC still suspect and or is there something else to check/replace? Also, since this is intermittent, doing the electrical checks as outlined by Wolfmeister would have to be done when this thing is acting up, I'm assuming when it's working ok, the electrical checks would also be ok.

 

Since the sensor system is a closed loop you should check all sensors. Begin with the EEC engine temp sensor as this is known as the "master sensor" to which everything is calibrated. Get it up to normal operating temp and then pull the wire off that sensor and see if your problem goes away.

 

I just wanted to add a note. I had to buy my IAC from a ford dealer and one dealer wanted $113 while another one down the road for $101.... So i guess different dealers charge different prices... and second the reason I had to buy it from a dealer...


I have a 98 XLT with the the SOHC 4.0L, 4X4. I originally ordered through NAPA (Never Any Parts Around) and after a week of no show and no tracking number they refunded my money...next stop RockAuto.com, They had it for $66, and recieved it and it was different than the one on mine. So I called them and they did some checking and was told the SOHC one could only be bought at a Ford or mercury dealer. The Ford dealer part number is 97JZ9F715BA.

Hope this Info helps someone and save you three weeks that is cost me...

 

autozone has it for like 72$ with tax and everything good comparing with 120 from dealer