928 Enthusiast

Hi all,

Does anyone have a method of bench testing an Idle Stabilizer? Or possibly know of any specs for resistance on idle stabilizer windings?

The manuals do not give any specs.

Thank you!!

Jay Wellwood

The reason that the manuals don't offer any specs is because the Idle Stabilizer is a variable type of valve.

In other words - the Stabilizer come preset from Bosch with a specific closed and fully open position. The LH unit (or other - pick your poison here) sends a signal poportional to the air flow as being registered by the MAF and corrected by the O2 sensor feedback as to actual voltage being sent to open or close the Stabilizer (given that the engine is not under any loaded condition as inputed by the Idle/WOT switch). So, as the speed sensor relays the engine speed, and the Idle switch is still active, the MAF sends it's input to the LH unit, it will vary the Stabilizer somewhat to either increase or decrease voltage to either raise or lower the contol voltage (ie valve position).

Probably the best you can do is to ensure that the Stabilzer is free to move in both open and closed directions and clean. I used a 12v source on my Stabilizer to ensure that it moved freely - whilst spraying the valve with a cleaner to remove any gummy buildup.

hth-

Steve J.

Thanks Jay - this is good information. I am reassembling and installing my intake tonight and I was wondering the same thing. I stuck a probe into the idle stabilizer and gently moved the actuator to be certain it was free. I will connect 12V to see if it moves. What sort of preventive maintenance can I do while I have it out? What kind of cleaner? Leave it dry or spray lubricated? <img src="graemlins/a_smil17.gif" border="0" alt="[blabla]" />

Mike Schmidt

The computer sends a signal to the idle stabilizer that pulses and changes in frequency, not in voltage. When on the car, the idle stabilizer can be checked with a dwell meter or duty cycle meter. The meter should indicate a fairly steady reading at idle with all accessories off. Turning on the lights and/or fan should show an increase of the dwell meter reading, and the idle speed should stay the same.

I can't remember if I used brake parts cleaner or carburator cleaner on my idle stabilizer when I had it off. I sprayed it and moved it back and forth until it was clean and moved freely. I think that most bad idle stabilizers are just stuck from the buildup that forms on them. Either that or maybe burned out after a while of being stuck, with the fuel injection computer continuing to send more and more of a signal to them in trying to get them to move.

Steve J.

The signal is a constant 100 hz. that is pulse width modulated (the duty cycle is varied). The valve/armature is too massive to flutter at 100 hz. It responds to the average voltage (depending on the duty cycle).
I cleaned my idle stabilizer with brake cleaner (no residue) and compressed air. Then I sprayed some WD40 into it and blew it out. It looks shiny and clean inside. The valve rotates very smoothly - no sticking or gritting.

928 Enthusiast

Thank you everyone this is exactly the information I needed.

Much appreciation.

Earl Gillstrom

WD40 seemed to help the idle stabilizer on my '88 5 Speed but not make it completely reliable. The Idle would still fluctuate a little bit at times.

A few months ago I tried Kano Penephite <a href="http://WWW.KANOLABS.COM" target="_blank">WWW.KANOLABS.COM</a> which is a penetrating oil with graphite. Now the idle is rock steady all of the time.

I removed the mass air sensor and sprayed it in the hose to the stabilizer and then installed the mass and started the motor for a few seconds and then shut it off for overnight to let it soak in.

Jim Morehouse can monitor the result, he bought the car last week.

Earl Gillstrom '91 GT and '88 auto parts car

John Veninger

Hi Earl,
Welcome to the board. I see you now own a GT!