I'm about ready to pull my hair out.
I replaced my idle control valve and also the DPFE on my 1999 2.5 Ranger.
The Idle valve wasn't making any noise, I just thought after 135,000 miles it would be a good idea.

After replacing the valve and DPFE, then pulling the negative battery cable, turning on the lights and waiting for an hour, I drive it for about 40 miles.
When I came to a stop, it would hang at about 1500 RPM for about ten seconds and then immediately drop to about 800.
I measured the voltage at the plug coming into the valve and it was about 14 volts.
I measured the resistance of the valve and it was about 10 ohms.
Turning on the AC made very little difference in RPM.

So, I put the original Idle valve back on.
The idle dropped down to about 1000 rpm almost right away. Much better.
But, when I pull the connector while it's running at idle, there is no change in RPM. And, when I turn on the AC and then pull the connector, the RPM's drop.
I read that whenever the Idle Valve plug is pulled while running, the engine would slow or stall.
It doesn't slow unless the plug is pulled while the AC is on.
Is this normal?

Also, the RPM will not return to 1000 unless I am at a complete stop.
If I let off of the gas, put it in neutral while and the truck is going 3 MPH, the RPM will stay around 1,500 RPM.

The throttle body and butterfly were cleaned using throttle body cleaner.
The butterfly does not stick.
Other than this problem, the truck runs like new.

I'm completely lost.



Thanks in advance.

 

Welcome to FTE. Has your "Check Engine" light come on? If so, get the trouble codes and post them. What made you change the DPFE? From my own experience, I know idle problems sometimes can be difficult to solve. Let us know.

 

I'm wonder if the ECT sensor(coolant) is throwing your 'puter a curveball, and telling it that the engine is still cold? Is 14 volts correct for the IAC-most sensors run on 5-8 volts? I could be wrong?? The ECT could be worn out, and not doing its job correctly..Let us know what you find.......

 

Sounds like you've been busy doing some preventative maintenance.

I like michigan66 idea to to scan the computer for trouble codes, do it even if you don't have a CEL lit, as there may be pending codes stored that have yet to set a trouble light.

Right now, with out any more clues, I'd maybe suspect a vacuum leak some where & given the vintage of your ride & it's mileage, the PCV valve & it's rubber plumbing probably belong on your suspect list, along with the vapor recovery & brake booster vacuum lines, maybe even the Hi/Vac controls & intake manafold too.

So without further clues, I'd consider doing some some vacuum leak trouble shooting.

Let us know what you find.

 

had the same problem with my Ranger. I tried choke and carb cleaner also. I solved it by spraying the shaft and plunger with WD40 and wiping down with cutips. It is still working fine after 20,000 miles