THSCC Forums

Amy's truck (93 Ford Ranger) has a surging idle when cold. One possible suspect is the idle control valve. I want to know how to test the valve.

I'm not asking how to test the effect of a working or nonworking valve on the running of the engine.

This valve has two electrical connections. No vacuum connections. How do these things work? (I understand that they let air past the throttle plate, I'm not asking about that, but rather the mechanism.) Do they open fully at 12 volts, and halfway at 6 volts? Or do they flutter open and closed, with different open-to-closed ratios for different effect?

Lots of internet search says "clean them" but nothing actually tells me how the mechanism operates.

Anders

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Lina Racing: As Seen On Radio

Anders, this may not be much help - but from my experience with Bosch ICVs on BMWs I understand that they are open or closed only. On my car, if you turn the key on but don't start the engine, you can hear/feel it "rattling", which is the valve opening and closing rapidly (like numerous times per second). On BMWs they stick and cause oscillating idle like you describe. The "word on the street" is that cleaning the BMW ones just makes it worse. I think for my car it's like a $70 part.

YMMV.

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Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

Anders,

When I was out of town a lot last year, Kelly's 97 Mustang V-8 developed a problem where it wouldn't hold an idle after cold starts. She took it to a good shop who tried cleaning the Throttle Body and maybe the Idle Control Valve. Didn't solve the problem so the Valve got replaced. Problem went away and has not returned.

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Dick Rasmussen

FS 50 2018 Mustang GT

Mazdas use an electromagnet/solenoid (probably similar to the Ford part since Ford owns part of Mazda) that is pulsed by the ECU to control how much air is bypassed the throttle body. Apply 12V and it will fully open, 0V and it is shut. I haven't observed opening percentage under fractional voltage on mine, but it should work.

I'm looking at the Factory Manual for my RX-7 and they list a voltage being applied of 8-11V with ignition on. Idle voltages range in 5-11V and it shows a "wavy" scope pattern (think absolute value of a sin function or a bunch of semicircles in series) with 40 milliseconds between points where it bottoms out at 5 volts.

Duty cycles are as follows...
Cranking: 99%
Idle: 32-65%
Initial set: 38%

Fuel injectors should work on the same principle as this device.
I tested fuel injectors using a 9V battery and got an elementary flow rate (not using a precise graduated cylinder) consistent with 75% flow if that's worth anything to you.

Hope that helps...

Anders,

I just checked a manual for 97 Fords. As Ashraf noted, it is a solenoid actuated valve which is controlled by the computer. The manual didn't give actual duty cycle examples like Ashraf's Mazda example. However, it did mention duty cycles. Ford says that they cannot be cleaned.

Thinking about duty cycles and how often it is cycled in normal driving, I would say these probably simply wear out and either allow too much air or they start binding.

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Dick Rasmussen

FS 50 2018 Mustang GT

Which engine? The 2.3L four banger that Ford used for years or a V-6?

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Has no responsibility whatsoever.

The V6.

So, it sounds like these devices are pretty "dumb" and I'll be able to test it with just a battery to see if it can even still move. Good.

Anders

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Lina Racing: As Seen On Radio

Careful. My Ford manual mentions a "sensitive" diode in some.

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Dick Rasmussen

FS 50 2018 Mustang GT