Thanks Kyle and 190D for your advice. I probably am due for a motor mount changeout and I'll bet that will solve most of my rough idle problem. Although it starts, runs, and shifts extremely well, It seems there is more driveline windeup when I shift sometimes than other manual tranny cars I've driven. I'll bet the tranny mount and engine mounts could use replacing. I'll check these next weekend when I replace the fluids.

I've also noticed that the car shakes quite a bit when I turn the key off. Is this normal or another symptom of bad motor mounts?

As far as the GP light not coming on, it really is strange. It will start very easily if the outside temp is above 40 or so, but the GP light just doesn't come on below that. I replaced the battery yesterday to an Optima. The car would crank OK, but there is no record of when t he battery was last replaced, so I thought it best to just replace it for peace of mind. It's supposed to be very 2cold tomorrow and Monday, so I'll see if it is just a battery issue or not. Then I'll do more troubleshooting of the GP and GP relay. Still, the car cranks fine when cold and starts very easily when the GP lights come on. I don't have to wait much at all after the GP light goes off. As soon as it goes off, it will start right away.

Could only 1 bad glow plug cause the light not to light? Are they in series or parallel?

190D, I have noticed the idle behavior that you are alluding to: sometimes when I come to an idle it doesn't idle very smoothly but once the throttle is "bumped" a little, the idle smooths out nicely. The only explanation I have is maybe excess fuel in the deceleration process has cooled a combustion chamber sufficiently to prevent the idle charge from lighting correctly. Since that cylinder is not burning in a timely fashion, it is not generating enough heat to raise its temperature for the next fuel charge. Bumping the idle and then letting off the accelerator seems to cure the problem. I've run a couple tanks full of Techron through the car and it is much less noticable now. I still think I could bump the idle speed a bit.


190D, with the 15W40, you don't have any cold cranking problems? The manual recommends 10W40 down to -5 deg F, but the other oil weights in the owner's manual aren't really common anymore. Everybody wants to sell 10W30 or 5W30. These aren't really appropriate weight oils given the recommendations in the owner's manual.

My car is navy with a navy MB-tex interior. I have a sunroof, power locks (don't really need), power windows (don't really need). The climate control works, and the A/C has been converted to R134. There is no rust on the car except I found some under the battery tray when I replaced it last night. I've washed it twice and have found zero water leaks anywhere. Overall, I'm very happy with the car. It really runs and shifts well.

I also got > 40 MPG on my first fillup last night. I've been running it pretty hard with about 75% highway and 25% city driving.

As far as Mercedes Benz go, it is obvious that this is a more modern car than others I've owned and driven (108 body cars, 116 body cars, 123 cars). It is a little "light in the shorts" relative to the 108 car I also own: meaning that following a semi it gets blown around a bit. But, the suspension is really quiet and smooth and it handles much better. It really is a great daily driver.

Thanks for the advice. If I need future help, I know where to go.

Sholin in Mustang, OK

__________________
What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.