Hey gang! I've been having problems with my 98 3.0 Ranger since the cold weather started. It didn't want to start and would idle real low. Had the battery and alternator checked at Autozone and they tested fine. Guy there said maybe it was my cold cranking amps. I went ahead and replaced the battery. Went to go to work last Friday and it would barely run. Battery icon gauge(name escapes me) was halfway b/w low and the middle. Went to work b/c it worked fine after a few minutes drive. Went to leave work where a buddy was going to look at it. Got it where I needed to go, a 1 min drive and it died. Started it, as it was in a road, and got off said road and it died again with battery gauge on L. We went ahead and replaced the alternator. No problems until today. Went to leave work and it barely ran, RPMs of @500 at idle. Normal is 1000-1200RPMS. Went and topped off on gas as I was low. Still had 3.5 gallons in the tank. Drove back to work, CEL popped on as I was parking. Drove home and hooked it up to my OBD II scanner.
It threw a P1507 code, which I know from looking it up should be the IAC valve. The weird part is that is not the text that was under the error code. The text was : Manf Cntrl Veh. Spd Idle Speed Control Auxiliary Inputs.
I put that text into Google and got a bunch of hits. All of them were in the language of the Shadetree Mechanic, which I still haven't mastered. Can someone translate it and tell me what it means to me? I should note that none of the hits off google seemed to relate to Fords.

 

Regarding the P1507 code, change the IAC valve.

 

he's right. It's the IAC valve. I just had the same problem and changed out the valve and the truck idles like new. They cost 49.00 at AUTOZONE which is half the price of the dealer. Takes 5 minutes to do it. I have a 2001 ranger 3.0 ltr and it probably is the same as your 1999. If you need help you can call me at 636-346-3704

 

I replaced the IAC valve, quick 5 minute job. I also cleared the DTC so we'll see what happens after she sits for awhile. That's normally when trouble occurs.

 

Everything seems okay. I have noticed that at idle(now normal at @1000RPM) with the AC on, it races @100 rpms every few seconds. Don't recall if this was normal before or not.

 

You might want to see if the A/C compressor is actually engaging.

The computer automatically operates the IAC valve to anticipate the added load of the compressor. If the compressor is not engaging and placing that load on the engine, the idle will rise as you've noticed. Since you said it's doing it every few seconds, an abnormally short engagement time, I'd suggest checking the A/C system's charge level.

Sometimes on EEV-IV systems, it's a good idea to completely reset the the computer then force it to relearn idle strategy from scratch.

Steve

 

I like the "reset the computer" idea, any time we replace, or rework a sensor.

As the computer gets all confused if we don't, because it's been adjusting it's operation with inputs from the old controls/sensors & now all of a sudden we put a new part on thats performing different, or outputting different to the computer, so if we don't tell it, by resetting the computer, it gets all confused.

On the IAC, I recently had mine act up, it was sticking & causing a higher than normal idle when coming to a stop.

So I removed it & cleaned it up with WD-40 & a Foam tipped swab (don't use a cotton swab, as it's linty).
A spray plastic safe cleaner with a recipe for cleaning MAF sensors would likely be a good choice too.

So if money is tight, you might try cleaning it, maybe it'll buy some time.
Cleaning it seems to work for some folks, not for others.

Just keep the "cap" that has the little air filter in it, facing up, so any crud loosened by the cleaning, doesn't get into the IAC's air filter.

Mine was hanging up from carbon depoits, where the operating shaft, goes through the baffle into the solenoid end,(the electrical connection end).

It's been about a month & a half since cleaning & all is still well.