Idle control valve

Hi folks,

I have discovered that when I disconnect the Idle speed control valve, the engine does not die and idles like with the valve connected. This is a bit strange I have changed the valve and it works the same way. I could not find any hole in vacuum pipes, no additional "sucking". EGR works fine. No codes stored in PCM. The same situation is after disconnecting the battery for a reasonable period. I tried to play with the screw under the throttle to set the "closed pos." correctly as well. No change.

When I disconnect the Idle valve and connect it back after a while, the RPM goes a bit up (aprox. +300RMP) and returns back to normal idle.

Is this situation normal?

Thanks for any hints, MarPac

Because you get the same results with two different control valves, I would suggest that so much air is by-passing the throttle plate, even in the closed position, as to make the air flowing through the control valve irrelevant.

Could be that the throttle body is a bit worn where the plate-edge nearly touches the body. The stop-scew is intended to never require adjusting. Says who? As the vehicle wears on for many thousands of miles .... it will likely require adjustment. It is often best to replace the original screw with a bolt/screw with the proper threads. By removing the throttle body and holding up to sunlight ... we can make the stop-screw adjustment to the plate that ALMOST shuts of all by-pass air.

Probably the throttle might have a leak in closed pos. When I screw out the end position screw I can feel the throttle can stuck in the closed position so I have push it a bit to open.

How to check the idle speed valve? There is aprox. 10Ohm resistance. If I put 12V on it I can feel the coil is trying to move the pin, but the pin does not move at all. I can move the pin manually slightly.

Hi MarPac,

Disconnecting the IAC valve on an engine at normal temp should cause the RPM's to drop slightly (to around 500 RMP's at idle), so I think you definitely have a problem.

You didn't post what year is your windstar, but I would make sure the gasket for the IAC and throttle body are OK and the bolts are tight.

If I remember correctly the manual specs a resistance of 8-13 ohms; however such reading does not ensures the IAC is ok and the even manual says so.

Oscar.

Ford Windstar 3.0 96.

Well, I have cleaned the idle valve and have reset the ECU. The Idle is good now, shifts well, drives good but after engine start the RPM goes immediately to 2000RPM and than goes down even the engine is warm.

When idling, I can disconnect the idle valve connector and almost nothing happens(RPM goes down a bit, let me gues 50RPM). When Idling with gear selected (D, R, 2, 1) and removing the idle valve connector, the engine almost dies so it seems that the valve is working. (the engine needs more air)

I could not find any vacuum leak. All the sensors seems to work properly checked with diagnostic. Is it possible that Trans range selector sensor might do this? What about the vacuum pipe sucking the rear valve cover? (The pipe itself is OK.

It seems that there is some additional air flow into the intake manifold :-( but where?

The throttle is in good condition. I saw that there is a small hole (aprox 2mm) in the throttle plate.

Ford Windstar 3.0 96.

I saw that there is a small hole (aprox 2mm) in the throttle plate.

Are you saying there is a drilled hole in the plate? ..... or are you saying there is a 2mm gap between the plate edge and the body barrel in the closed position?

A 2mm gap would be a million times too large. The plate edge should almost touch the barrel .... holding the throttle up to sunlight should show just the tiniest bit of light coming thru.

So, I took the idle valve from my Ford Scorpio and it seems to be OK. The problem should be the valve itself. The coil inside is OK and the valve is somehow working, but not when idling engine without any load.

Does anybody know how the valve operates? It is not a servo. Seems there is some rubber plate inside the coil and the coil sets the vacuum to be on the first side of this plate (valve closed, coil under power) or opposite side (valve opened, coil without power). So the coil does not move the valve pin itself. So, usually this rubber stuff inside breaks down and the valve is not working, even the pin moves well and electrical connection has appropriate resistance.
I'm I right?

As about the hole, the small hole is directly in the throttle plate, the whole plate fits perfectly inside the throttle body and has no space around. Maybe it's just only in 3.0 version as I can see almost all the Americans uses 3.8 and more :biggrin: You know 3.0 is even too big as usual in Europe :runaround:

The IAC valve is PWM controlled, kinda like a servo. Depending on the duty cycle the pintle will move more or less.

I still think you might have a vacuum leak but since I've never seen the 3.0 engine I can't tell you what else to look. I'm sorry.

Have you tried a propane torch to find leaks? What happens if you block the air tube while the engine is running. Will it die instantly or still keeps idling?

Oscar.