A/C High Idle ??

desertt5 · 07-07-2008, 11:42 AM

Hi all,

My 87 S idle really drops when the A/C is turned on. Normal idle is around 950 warmed up or so, with A/C on its closer to 550 or so. Tries to die or does die when you let off the gas.

Is there a high idle circuit / switch? Been looking at vacuum lines, and so far all seem to look good?

Thanks
Kirby

onZedge · 03:56 PM

Yes, there is an input to the DME when the A/C is turned on. What kind of car do you have. A 924S or 944S? They made both in '87 (at least I think they did). EDIT: They did make both in '87.

gtroth · 07-08-2008, 06:18 PM

For 944S, you might confirm your ISV is working - it is supposed to open some when AC is on to hold idle constant.

desertt5 · 07-09-2008, 03:58 PM

gtroth and onZedge,

Thanks for the help. Sorry it is an 87 944S.

After reading your replies I searched on the LSD some at work today. Says you should be able to feel it vibrate with the key in the "on" position but not running. Mine is dead like that.

Also read that some folks have sprayed cleaner in thru a vacuum line and been able to get it going again. Couldn't figure out which line they were able to use (get access to). Will be playing more with it tomorrow night.

No idea in the world how they were able to take it by its self either ?( intake still on)

I will check the DME signal tomorrow. I should be able to read a difference with a regular DMM from what I read today.

Man, this place is TOO cool !!

onZedge · 07-09-2008, 05:33 PM

You can check the ICV without taking off the intake manifold. With the engine off, carefully remove the plug from the ICV. You have to carefully pry back the spring clip on both sides of the connector - don't lose it! (If you haven't done this before, it will become clear when you study it for a few moments first)
Using your DMM, measure the resistance between the center pin (on the ICV) and each of the two other pins. I think it should be 40 ohms each. Now measure the resistance between the two outer pins. Should be the sum of the earlier readings, or 80 ohms. Now check the wiring harness connector center socket voltage. You should have battery voltage between any engine ground and the center connector socket (with the ignition switch ON).
If your readings agree with the above, the ICV is probably electrically sound. It will NOT tell you if the valve is sticking mechanically.
I test the ICV using a 9V battery. Connect the (+) to the center pin of the ICV and alternate the (-) between the outer two pins (just tap the outer pins with the (-)). This should open and close the valve. If it doesn't...many have had good luck squirting carb cleaner down the inlet hose while the car is running to un-stick the valve. Again, you don't have to remove the intake manifold to do this. Tight space to work - you'll see what I mean.

desertt5 · 07-10-2008, 04:29 PM

onZedge,

Checked out the LSV today at work. Mine has 2 pins vice 3. Looks like its a different version for the S models maybe.

It ohm'd out to 8.4 ohms between the 2 pins. I do have battery power on one of the pins from the DME going to the LSV. Is this too low for this style LSV?? I know 8.4 ohms is good for most of the coils/ relays I deal with at work, hopefully this one too.

I am going now, car finally cooled down from drive home, to work off that inlet hose and get some cleaner down to it hopefully.

Thanks again

desertt5 · 07-10-2008, 06:22 PM

Seems to be working like it should now. Now to tinker with some more things.

Thanks onZedge and gtroth for the help.

onZedge · 03:28 PM

Quote:

Originally Posted by desertt5

Seems to be working like it should now. Now to tinker with some more things.

Thanks onZedge and gtroth for the help.

Sooo... squirting carb cleaner down the hose was your fix?

ICV = Idle Control Valve. What is a LSV??

gtroth · 07-15-2008, 04:11 PM

--he meant ISV. On the 16V engines, its ISV (idle stabilization valve) not ICV, by the way.

desertt5 · 07-16-2008, 01:55 PM

Thanks gtroth, I did mean ISV not LSV.

Yep, carb cleaner down the inlet did the job for me. I had read on another post that someone used Seafoam lube and it worked also.

This weekend I have to try to fix WHERE it wants to idle at. In the mornings it starts at 1800 until warm, then goes to 1000 or so and seems to stay there. Outside temp is ~65F.

Afternoons, idles right of the bat at ~800 and stays there all the way home when idling. Outside temp ~90F.

A/C does not seem to effect the idle by any more than ~50rpm's at any time.

Being my daily driver, I don't have much time after it cools down to mess with it, and don't want to start putting it back together at midnight.

Would help some too if I could find the diagnostic plug. I have looked all over, especially around driver side/ brake booster area.

gtroth · 08:26 AM

I'd check the TPS - make sure DME is being told to idle.
Then go hunting for vacuum leaks.

desertt5 · 07-16-2008, 08:17 PM

I will look for a way to check the TPS tomorrow at work. I think I read one already, something about it being at idle or not at idle. I also remember something about the DME signal. Just have to hunt it down again.

I seem to have lots of time lately to read on here during the day.

I am sure I won't be doing much on it til the weekend. Will let you know if I find anything.

Thanks.