At wit's end over an idle issue

[troylatif]

Hi all,

This post is to follow up on a previous post I created to discuss an idle issue I'm having with my 1985 380se. I've been through a lot of work in dealing with the problem and I'll list it out with steps that I've taken.

- I've tested the throttle position switch in the throttle wide open position and the throttle shut position. Both close the continuity tester.

- I've found a blown resistor in the Idle Control Unit. I've replaced it twice with no luck. The idle still rides high.

- I've replaced the idle control valve. I tested the old one; it bounces up and down between 32 and 50 ohms. The one I received sits well at 5 ohms.

- I've tested the voltage across the nos. 2 and 4 pins on the Idle Control Unit connector. I get a solid 12 volts.

- I had my parts supplier send me another control unit because the first I suspected of being shot and to no avail, the one he sent also had no effect.

Could it be a vacuum leak somewhere? Could it be to do with the switchover valve; the one on top of the driver's side fender under the hood.

I tell you, this problem is such a mystery. It started randomly one morning when I was driving out to work. I momentarily pressed the gas and I felt a sudden jump in power and since then the idle's been running at about 1600 - 1700 cold and between 2000 and 2300 warm.

I've almost considered just playing with the timing to get it to come back to normal, but I think that'd really mess with fuel economy. So far it makes between 16 and 17 city and 18 to 20 highway. I used to get 19 city consistently when I came out to Texas. Before coming out here I used to get anywhere between 22 and 25 mpg in the Arizona desert.

I appreciate any insight you guys can provide.

-Troy