Another 4.0L SOHC Idle Problem

[enjr44]

If you don’t want to read the entire BS, jump to the last two paragraphs.

Back story: I got this 02’ Ranger in Oct 2001. Ford did the 30K and 60K servicing. It has 84K on it now. Other than that, only normal maintenance has been performed. It is as delivered and no repairs have been needed. For the last two weeks I have been in the California Central Valley. Temperatures were well over 100 most days. Since I had my four-legged buddy with me, there were times when the Ranger sat and idled for up to an hour to keep him cool. The temperature gauge never moved during these times; but, the outside temps around the truck were well over 135 several times.

On the last day of the trip back, I noticed that when I shifted from drive to park the idle would drop to around 500 rpm. If you switched the AC on or off, it really jumped around. It stalled once when shifting from drive to reverse. This truck it has always idled when warm at about 750 rpm no matter what you did.

I am an old school hot rod builder and know very little about the computer controlled engine systems. So, I spent a bunch of time reviewing various threads on this forum and found that here seemed to be about a zillion sensors that affect the idle speed. Most of the talk; however, centered on the MAF and IACV and indicated that they could be cleaned.

This morning I disconnected the battery and cleaned the MAF and the IACV using MAF cleaner. The MAF looked like it had a small coating of something on the filaments. After cleaning they looked cleaner; but, not shiny like a new dime. The inside of the IACV was coated with black soot (carbon? - how does that get on the intake side of the engine anyway?). I wasn’t heavy like an EGR valve; but, everything was coated. Using MAF cleaner it cleaned up pretty well. Put the truck back together and drove it for a few miles. It idles when warm at 750 again and everything is back to normal.

At last, my question. Is it fixed? I know the takes a while for the ECU to relearn the engine. So can a do a victory dance now or do I have to wait and see?

Thanks, Ed

 

[Earl43P]

Dance.

 

[adsm08]

A light layer of black sooty build up on the intake components on pretty much any engine with EGR or PCV (both fairly standard issue after 1975).

EGR should be obvious in terms of how it causes this.

PCV is used to pull blow by, effectively exhaust gas that gets by the rings and into the crank case, out of the crank case to keep it from becoming pressurized. Since the intake is free vacuum the PCV valve is hooked to the intake, and that little bit gets pulled back in to the intake.