idle control valve buzzing with car off

[nealf2002]

I just walked by my '87 in the garage and heard the buzzing. I didn't drive the car today. Wonder how long its been on. I unplugged it for now but does anyone have a clue why its stuck or what I can do to fix it?

Thx

NF
'87 Carrera

[steely]

This means that the DME is on for some reason, providing +12 and pulse-width modulated grounds to each of the 2 windings.
The DME is powered by the DME/FP relay, which is powered by the ignition key.
You could pull the DME relay and see if it stops (it should).

With the relay out...
You can check the DME relay socket for +12 at pin 86.

This will tell you if power is getting to the relay turning it (and the DME) on.
Check for +12 on socket pin 87 as well (the power path to the DME).
Both should be dead, but something is wrong obviously.

Or you can check known HOT always points on the fuse panel.
Let us know.

on edit - please be careful - you may have power running around where you least expect it.
The DME relay may be hot.

[steely]

Your fuel pump isn't/wasn't running, was it?
how long have you have the car out of curiosity?
not picking, just trying to get a handle.

believe or not, some hack the FP wiring to make sure the FP runs, and if done incorrectly (as if there was a correct approach to this), it could back-feed the DME.

If the FP isn't running, that's another clue, but be aware that the hot side of the injectors could be live if the DME is really on.

[rick-l]

Subscribed. I'm wondering how it shuts off if the DME is always on. I guess the ignition comes from a different source.

[steely]

The ignition switch controls power to the coil, the DME just controls the timing of the coil output. I don't know if there is more beyond that.

The DME can be also on before you start when the key is on too, by virtue of the DME/FP relay, but the FP won't be on until you try to start the engine.

[steely]

cool link: The DME Relay explained - Dorkiphus.net

[rick-l]

Originally Posted by steely

The ignition switch controls power to the coil, the DME just controls the timing of the coil output.

The ignition coil is powered from a wire attached to fuse box 1 fuse #8 and is powered whenever the switch is in run or start.

The power that energizes the DME relay comes from a wire hooked to fuse #9 (electrically the same point) but goes through the alarm control unit

If that is any help.

[rick-l]

The fuses mentioned in the above post are where the wires come from. They are on the hot side of the fuse, not protected.

this

Originally Posted by steely

You can check the DME relay socket for +12 at pin 86.

[nealf2002]

So how do I get it to stop buzzing the right way?

[steely]

Updated..

Rap on the DME relay with a screw driver handle lightly to see if it is hung up, or
Just swap the DME relay with a known good one. You might want to disconnect the Neg side of the Battery before doing this.

If that doesn't fix it, then...
Make the measurements in Post #2 and let us know what you find.
PM sent if you want to contact me, I'm over in Horsham.

I have a hunch your DME is remaining on for some reason, and it could be related to the relay that usually powers it.

[nealf2002]

Pulled relay, reattached. Still nothing. It is humming still. Ordered new relay. Will start testing.

[ischmitz]

Let's assume your dash light didn't stay on (you'd notice the oil and alternator lights) This more or less clears the ignition switch.

It leaves the DME relay or the alarm unit that has an internal short. Did you pull the DME relay and confirmed it stopped the humming?

Next, pull the DME relay and measure terminal 86 inside the DME relay socket against chassis GND with a test light or voltmeter. If you see +12V you have an issue with the alarm unit or harness. Then check if the DME relay stage 1 is short (stuck contact): pull it and measure resistance on the DME relay pins between terminals 30 and 87, if you see a small (~ 1 Ohm or less) value it's stuck and needs to be replaced.

Ingo

[nealf2002]

Uh, no. I disconnected battery, then pulled the relay and inspected it. Are you saying I should keep battery attached and they pull relay and see if that shuts off the ICV? Is there any damage that could occur by doing so?

Thanks for all the help as I'm clueless..

BTW I drove the car around a bit and it seems totally fine and normal except for not cutting the circuit to the ICV.

I did test the battery
Last night and got 13.xx

With the ICV running it dropped down to 11 or 12.xx

[nealf2002]

Received my new Pelican DME relay. Took the old one out. It was warm to the touch. Must have been hanging up as others said. Put new one in, no more humming ICV. Thanks for all the advice.

[T77911S]

carry it as a spare. you know it works.