Testing the Air Stabilization Valve.
 

Hello Everyone,

I am about to root through a cold-starting problem on my 87 924S and was wondering if anyone knew which of the three terminals on this component I need to use when checking for correct dwell readings.

Thanks Very Much in Advance,

Interesting. The idle positioner on the 87 944S looks like it has only two terminals.

The other post 85.5's have three terminals on the idle positioner.

Both are reported on the schematics as a motor device -- a black rectangle.

The 944S has one rectangle indicating a single motor with just two terminals. This could be a rotary solenoid thus requiring a pulsing of the current to it to keep the valve open.

The other 944's have two rectangles (motors) wired in such a manner as to allow the valve to be driven either way by applying current to the correct terminal. A third terminal, between the motors, goes to ground.

The testing procedures indicate that the 944S idle positioner receives battery voltage on pin 2. The DME "pulses" the current to ground through pin 1 at an average of 100Hz with the engine at running temp. You should be able to feel and hear the valve vibrating (pulsing).

Turning on the AC or other electrical devices that will load the engine should result in a change of the pulse frequency. As this is a pulsed 12 volts you should be able to use a dwell meter to check it like one would check the opening/closing of a set of points in an older style distributor. What do you get as a dwell value when your engine is at average operating temp?

Hmmm.....

Meaning???

Not quite awake fighting a head cold. Got diverted looking at the differances.

As the 924S and the 944's for this year range use the three pole reversing motor design I didn't see the connection to dwell.

The 100 hz signal I can see a relationship to dwell.

Not getting out of this that easy.

Thinking that since the manual shows a 100hz square wave for the single motor 944S, the 944's and the 924S's would have their two motor valves driven possibly in the same manner? thus the question about dwell (frequency?).

Hey, thanks for the help folks. I haven't had a chance to check this out because my car now has a fuel pump problem that takes precedence, but I will get to it and post whatever findings I get. I do so hate a car that runs poorly when cold. Thanks again.

A cold start fuel delivery problem may be the fuel pressure regulator more so than the fuel pump.

SoCal, your point about the fuel pressure regulator is a good one. I will check it's function as well, while I'm at it.. I actually suspect that my fuel pressure was poor to begin with because of an issue with the fuel pump itself. The pump had been leaking through on of the electrical terminal posts (sort of odd) so I am waiting for the replacement now.