Another Idle Issue

[86 911 Targa]

Having done a search for idle adjustment,
followed the instructions per the Bentley,
I have an issue on our '86 3.2.

Idle Adjustment:

1. The engine idles at 750 rock steady.

2. Key on, engine not running, the ICV does vibrate.

3. Engine running=750 Rpm's

4. Turn engine off, short B & C on the engine fuse
panel connector.

5. Idle increases to 950 Rpm's without any adjustment.

6. Turn engine off, remove the shorting wire from the
panel connector, idle returns to 750 Rpm's.

I'm trying to increase the idle to 950 RPM's.

Would cleaning the ICV resolve this issue?

Thanks in advance.

Gerry

[stlrj]

No, but backing off the idle air bypass would.

[rusnak]

I agree, the icv is just a pair of dc motors that turn a valve to let air bypass the throttle. It's controlled by the dme, so you can't do much to change it's settings short of buying a custom chip. But why you would want idle to be that much higher than spec? I think what's happening is that when you disable the icv by jumpering B & C, your afm bypass screw lets enough air by to raise idle quite a bit. Then when you let the icv operate, it's taking the rpm back down to 750.

One check you can do is to remove the icv, and with the engine warm, re-connect the dme plug and look down into the icv body. The valve should appear to be half open.

[86 911 Targa]

Originally Posted by rusnak

I agree, the icv is just a pair of dc motors that turn a valve to let air bypass the throttle. It's controlled by the dme, so you can't do much to change it's settings short of buying a custom chip. But why you would want idle to be that much higher than spec?

A/C load.

Spec is 850 RPM's.

I checked, and the DME (Pins #29, 33, 35) is compensating for A/C load,

as the RPM's only drop from 750 to 700 with A/C.

Also, other 3.2 owners have managed to adjust the idle using
the steps per my thread.

Should'nt shorting the two pins on the connector, center the ICV?

I'll follow your lead.

Thanks for your input.

Gerry

[rusnak]

Yeah, I know how to adjust the idle.

But you didn't say you were adjusting it with the AC switch turned on - that's an entirely different subject. I doubt you'll persuade the dme to go outside of it's programming, no matter what you do with the idle bypass. I can check to see how much my idle drops when I turn on the AC, if at all. I suspect you'll probably not be able to get 950 rpm with the ac turned on unless you want to hold the throttle down with your toe.

Jumpering the two pins de-activates, so to speak, the ICV. You can check it for proper function like I said, but there is no point unless you are not jumpering the two pins. The little valve will look like it's pulsating at half open. While it's out, just spray it with some carb cleaner until the black stuff stops flowing out. Let it dry first, then re-install.

[86 911 Targa]

Originally Posted by rusnak

Yeah, I know how to adjust the idle.

But you didn't say you were adjusting it with the AC switch turned on - that's an entirely different subject. I doubt you'll persuade the dme to go outside of it's programming, no matter what you do with the idle bypass. I can check to see how much my idle drops when I turn on the AC, if at all. I suspect you'll probably not be able to get 950 rpm with the ac turned on unless you want to hold the throttle down with your toe.

Jumpering the two pins de-activates, so to speak, the ICV. You can check it for proper function like I said, but there is no point unless you are not jumpering the two pins. The little valve will look like it's pulsating at half open. While it's out, just spray it with some carb cleaner until the black stuff stops flowing out. Let it dry first, then re-install.

The idle adjustment is being made with the A/C Off,
and the jumper in place as per my thread.

The issue is, the return of the 750 RPM's when I pull the jumper
after setting the idle to 950 RPM's.

I was hoping to get 950 RPM's W/O A/C, and 900 RPM's W A/C.

Also, you are correct, the DME cannot be changed,
and most likely, the ICV needs cleaning.

I'll clean the ICV tomorrow.

Thanks again,

Gerry

[rusnak]

Yeah, you might find that the ICV is dead, and is jammed shut. Hope it works out. Just for giggles, make sure the closed throttle position switch is working.

[86 911 Targa]

Originally Posted by rusnak

Yeah, you might find that the ICV is dead, and is jammed shut. Hope it works out. Just for giggles, make sure the closed throttle position switch is working.

The ICV does vibrate as it should, with the key "ON" W/O the engine running.

I'll also check the microswitch tomorrow.

Thanks again,

Gerry

[Jonny042]

I think the DME is going to shoot for 750/700 no matter what you do. Unless of course you adjust the air bypass so foar one way or the other other than the IACV cannot do enough to reach it's target.

Idle adjustment is going to be via programming.

[86 911 Targa]

Thanks All,

Rusnak, Jonny042, and stlrj.

The idle switch checked out O.K.

Rusnak, as per your suggestion, I cleaned out the ICV by spraying
cleaner with and without the ICV active.

There was not much "gunk" in there, but it does look a lot cleaner.

Re-installed the ICV>jumper>set the idle to 950RPM's
>pulled jumper>idle remained at 950 RPM's>turned on A/C
>idle drops about 50 RMS and is stable.

I'm O.K. with electrical, A/C, and other minor issues but do not
like to play "fingerpoken" with other 3.2 problems.

Thanks again.

Best,

Gerry

[rcaradimos]

When you take the idle screw out all the way it will look like the pic. On the screw you should have an o-ring to seal out air from leaking in from around the screw.

[86 911 Targa]

Originally Posted by rcaradimos

When you take the idle screw out all the way it will look like the pic. On the screw you should have an o-ring to seal out air from leaking in from around the screw.

Bob,

As per my last post, I think I'm O.K. now.

But will keep your suggestion in mind should
the anomaly return.

Thanks,

Gerry