I've searched this topic and have come close to answering my ???'s . . .
But what should the idle be?
And how do you adjust it?

My POS Haynes manual has been no help!

 

I don't believe it is adjustable on a '93. (I'm assuming this is the Ranger in your sig, but it would help to know for sure.)

IAC, TPS, MAF problems, plus vacuum leaks, etc. could cause the idle to be off- what's it idling at now and why do you think you've got a problem?

 

Right, the idle is not adjustable on a '93 (or any other year Ford Truck that has the 4.0L OHV engine, for that matter).

A poor idle is indicative of a problem somewhere. Some more information would help us better help you.

Have you tried pulling codes?

 

Yes it's the '93 Ranger. Idles, after warm, at 1100 - 1200 rpms. Pretty high.
I've only had the truck a month and it has always done it.
I've cleaned the MAF and just replaced plugs and wires, oil, filter, fuel filter, and air filter. If it is "choked", might be why I'm getting around 13 mpg!?

 

check your fuel pressure regulator for leaking fuel into the vacuum line. Also start your truck and listen for vacuum leaks. These will usually cause this condition. Another thing to check would be possibly a leaky intake manifold gasket, or like mentioned above, a faulty IAC valve.

 

Try the IAC first!

 

Actually, that is not true - there is a reset procedure for the idle speed, but it is not normally required. As was mentioned, the most likely reason for the high idle speed is the iac being sticky and needing replaced.

Here is the idle reset procedure (for the record):

4.0L Ford V-6 Idle Speed Setting Procedure
In some cases, the installation of a larger throttle body will result in an idle speed that is slightly higher than normal. If this condition occurs, the base idle setting will need to be re-set according to the following procedure. NOTE: Engine should be at normal operating temperature before performing this procedure!

1) Turn off all accessories & disconnect the battery for 5 minutes.

2) Reconnect battery. Disconnect the Idle Speed Control (ISC) solenoid located just behind the throttle body on the drivers side of the upper intake plenum.

3) With the truck in NEUTRAL, run the engine at 2500 rpm for 30 seconds.

4) Let the engine idle for 2 minutes.

5) Put the truck in PARK (or NEUTRAL if manual trans.) and adjust the idle speed stop screw until the idle is at 700rpm.

6) Turn engine off and let sit for 2 minutes then repeat steps 1-5 once.

7) Disconnect battery for 5 minutes then reconnect.

8) Reconnect the Idle Speed Control (ISC) solenoid.

9) Run the engine at idle for 2 minutes.

10) Quickly depress the accelerator pedal to the floor and release it immediately, allowing the engine to return to idle.

11) Lightly depress and release the accelerator allowing the engine to return to idle.

After carefully following the above steps, the engine should now have reset its base idle to factory specifications. The idle should now be smooth and at approximately 700rpm at operating temperature. If this procedure does not correct the fast idle condition, carefully check for vacuum leaks at the throttle body flange gasket and at the intake snorkel to throttle body interface. If no vacuum leaks are detected and the condition still exists, a condition that is unrelated to the mechanical throttle body assembly exists and must be diagnosed and repaired.

 

Fred, I believe the idle reset procedure you posted is for EEC-IV (pre '95) Ford vehicles. Things are different for the "newer" EEC-V systems:

https://www.ford-trucks.com/forums/4...-solenoid.html

Also, I think the OP was referring to adjusting the idle speed, as opposed to resetting the idle air trim values that get stored in long term memory.

 

That's possible - my source says its for all 4.0s, but since I've never seen the need to do it, I don't actually have experience and it may only apply to pre-EEC-V units. Sorry for the confusion. I'll see if I can get more info.

 

Where did that info come from? Maybe your source is correct and Ford just didn't put it in their manual(s).

 

on my 94 4.0 I did not go to all the trouble as listed above. I removed the throttle cover and held the throttle full open and there is a idle adjuster for the the throttle on the manifold. Just a plain ol screw assembly. My IAC is disconnected as we finally determined there is a bad wire in the system someplace and it causes the engine to race when warm and not idle down. Anyhow I adjusted the throttle stop screw restarted and checked the rpms, readjusted till it was at 7-800 and that was that.

I have not had any problems with the IAC disconnect even when runnng the AC and the idle rpms remain steady at about 600 unless I rev it up a tad then it will stabilize at around 700 with the AC on.

Look see if you can find the adjuster, it has a off the wall size head, 7/32s or something, cant remember its been a while.

 

The engine won't idle when cold with the iac disconnected, as that is the way that the engine gets more air. I know from experience that you'll quickly get tired of having to jack with the throttle to keep it running when its cold. It might be okay at warm ambients, but if its below 50 it will be a pain.

 

no I have not had any problems and it was in the teens this winter, like I said its been at a minimum of 2years like this. go thru all the emmisions tests and have no problems either. All the IAC is for is fast idle control when at an idle with drag on the engine ie. the AC, or heater in winter

 

"Teens"?! . . . in Tucson?! You must have thought the world was coming to an end! (lol)
Just havin' some fun with ya . . .
So I'm looking down the throttle body with the butterfly open, and there's a screw in there that will adjust the idle. A "stop screw"? Right?
I'm in a part of the country that gets "teens" for months. I'm going to unplug the IAC and try that as well.
Any way to test the IAC? Or will cleaning it like the MAF do any good? I hate to fork out for a $100.00 part just to find out that wasn't the problem.

 

I am having the same problems, i have cleaned the MAF, replaced the IAC and PCV. I have tried everything to correct my idle. I even disconnected battery over nite, no luck. It seemed to happen after pushing my truck to 105MPH. Which brings up another point, A 1997 B4000 i thought it had a speed limiter. Anyway this little truck won't be seeing 3 digit numbers on the odometer, Little too light at those speeds. The only mods i have are "CAI" and flowmaster cat back. Not getting any lean codes, any ideas would be greatly appreciated. LOL please no lectures on the speed, it was on an isolated strip of highway and conditions were clear and dry.