engine quits on low idle
 

When i have the idle knob turned all the way up the car is really shaky until the oil temp gets about 60c, at which point it smooths out and is fine.

I did notice though if i start to move the idle knob down, the car shakes violently even at a warm engine. I can turn it down a little bit with no problems, once the engine is warm, but if i turn it all the way down it starts to shake violently and sometimes will even quit (even at a warm engine).

Is this normal?

If not, is this usually a sign of bad compression or something as simple as motor mounts or a valve adjustment (typical cases).

I know this question has been asked before, but not really in this specific light (at least from what i could search).

Thanks!

Are your motor mounts ok? When they go bad they can cause some violent vibration.

Adjust idle
 

What Mercedes diesel equipped car has an idle adjust?

Are your valves are adjusted to the correct values? (all cylinders getting the most compression possible for even ignition)

What Mercedes diesel equipped car has an idle adjust? W115/W116

82' 240d. The motor mounts are not in the best shape.

And yes i was going to do a valve adjustment soon. But i just wanted to see if these would be the two main culprits beyond low compression in a cylinder.

Your '83 240D did before it received the turbo engine. I've never seen a 240D with a manual transmission that didn't have one.

OP: It could be a sign of many things, but you might want to start by checking the idle speed. There's a spec. If it's idling too slow, then yes it's going to be rough. That could be the result of badly adjusted linkage or base idle adjustment, or possibly something more difficult to remedy. It would be best though, if your valve lash is properly set, your motor mounts are in good condition, and your fuel filters are new before you start making any tweaks to the idle speed.

Most if not all older Benz NA diesels W123 included have a idle adjustment for upping idle until the engine warms up when it's cold out.

yes.. but the engine would still not quit most likely right? the fact that if i adjust the knob all the way down.. and the engine will quit.. i guess i am trying to figure out if that is normal behavior (before i continue going down the adjustments and whatnot).

I know for a fact i need to do a valve adjustment, and the motor mounts should be dealt with too. But, i just want to make sure that is normal operation before i begin..

just replaced the fuel filters, air filter, and oil change+filter.

No its not normal.... But a valve adjustment could help\fix it. It is a baseline procedure that needs to be done before further troubleshooting can continue.

If your idle is set too low, then yes, the engine can die. Can we assume that you've checked the glow plugs and found them to be working? The fact that you have this problem even after the engine is warming up indicates that they probably are not causing this problem, but that would be a symptom of faulty glow plugs during the warmup.

I heartily endorse the recommendations for catching up on all the typical "tune-up" jobs (valves, fuel and air filters, etc). Rough idle can have numerous causes, so start simple/cheap and work your way up. Checking the timing chain, checking the glow plugs, checking the fuel injectors; all these could be the cause or several together are contributing to the rough idle.

Valve adjustment and compression: You cannot get meaningful compression numbers until AFTER the valves have been properly adjusted, because a tight valve or two will CAUSE low compression, and the normal life of a valve is to GET TIGHT over time.

When you have the valve cover off for the valve adjustment, you can also quickly perform a rough check of the timing chain stretch by rotating the crankshaft until the camshaft mark lines up with the marks on the camshaft bearing towers. The camshaft mark is on the shoulder just behind the camshaft gear. Read the chain stretch on the crankshaft balancer timing marks. Search on this forum for how-to's / tutorials / guides, the job has been covered many times.

Idle adjustment: this is just about the last thing to touch, as the injection pump is rarely the cause of any problems on a Mercedes diesel of this vintage. Adjusting the idle at this point might be like putting a band-aid over a sucking chest wound.

Valve adjustment. For several months my 300SD would not idle when I first started it up unless I kept the idle pretty high with the accelerator pedal. Cured it when I got the valves adjusted. Went away immediately.