Need Some Help With A 380sl Problem

[Philoprof]

Came home from a 35 mile hwy trip in my high-mileage, 81 380sl last night. Pulled into the garage, turned the defroster off , and the car started misfiring and shaking, as the instrument cluster light dimmed and brightened. In addition, the garage filled up with exhaust fumes.

My first thought was the alternator. But the battery light didn't come on, I didn't notice the headlights dimming, and I restarted the car, after I had turned it off, In addition, it started it again the next morning, and ran perfectly, except for its usual, slightly, rough idle.

The following parts were all replaced, at one time or another:

Recently: Wires, distributor cap, rotor, coil, OVP relay, Idle Control Mod., plugs

Several years ago: Fuel pump, fuel pump relay, fuel filter, accumulator, head gaskets, chain, guides, valve guides, stem seals, etc.

Checked; Ballast resistors meet specs; Idle control valve meets specs and works fine

I suppose that one or more of the above things could have gone bad. And the only other things I can think of, which haven't yet been changed, are the ICU, fuel distributor, pressure regulator, thermo-time switch, and frequency valve --

The car is running perfectly again. But I suspect the problem will appear again, and I don't want to get stranded when it does So, I'm wondering if anyone could tell me what to look for now or when it does happen again.

Thanks very much in advance for any advice anyone can give me on how to deal with the problem.

Bill

[pawoSD]

Sounds like over voltage protection or voltage regulator on the alternator. Have you let it idle and put a volt meter on it to make sure its charging properly? Should be 13.6 to 14.1 volts at idle with a healthy system. Also, the idle should not be rough...what type of spark plugs are you running? They should be non-resistor.

Rough idle could be a sticking idle valve, might want to take it out and clean it if it hasn't been touched in a long time.

[Philoprof]

Originally Posted by pawoSD

Sounds like over voltage protection or voltage regulator on the alternator. Have you let it idle and put a volt meter on it to make sure its charging properly? Should be 13.6 to 14.1 volts at idle with a healthy system.

Thanks for the reply. I checked the alternator output, and it's fine.

Originally Posted by pawoSD

Also, the idle should not be rough...what type of spark plugs are you running? They should be non-resistor.

I'm running NGK non-resistors with Bosch resistor wires.

Originally Posted by pawoSD

Rough idle could be a sticking idle valve, might want to take it out and clean it if it hasn't been touched in a long time.

I cleaned the ICV out recently, and replaced the Idle control unit, because the idle was surging. So that problem was solved.

As for the problem I posted, someone in the SL forum suggested that the problem may have been caused by a defective switch over valve, which failed to properly advance or retard the distributor when I turned the defroster off, or by the distributor's advance/retard mechanism being stuck.

So, I applied 12V to the switchover valve, which caused it to click. But I still have to vacuum test it and the distributor to see if they're functioning properly. However, as the car's been running well, I haven't been able to reproduce the problem, and, hopefully, it was a fluke. But, as you know, these things rarely, if ever, just disappear.