My Dad's 300SE nightmare
 

Hi guys, my dad bought a W126 300SE at the beginning of last year and it has an issue which we have been unable to figure out how to fix. The engine cuts off at low RPMs both while moving (e.g slowing down for a turn) and when stationary (traffic lights etc), the issue is quite random and you cant predict when it will happen. it happens both when the engine is cold and warm; the oil pressure gauge drops to between 1-2 (out of 3) when at low RPMs and just bounces around those numbers before hitting 0 and the engine cuts off but it does not cut off every time the oil pressure drops and it does not always drop to 0. It also happens more often when the air-conditioning is turned on and the car is in drive or reverse. if anyone has any advice or has experienced similar issues with their car and has managed to resolve it please help us out. Thank you!

Oh mAN, sounds like a nightmare!

Hi,

this is a m103 engine, right? I have a similar problem, with my 260se. Exactly the same. I do think it is related to the electrics (mechanical parts almost all new, but old tubes). My guess is - distributor cap, sensors... I will look into this in the spring.

keep me posted,

blaž

AIC
 

If you still have the car, check the Air Idle Control valve. Those symptoms are typically caused by the AIC. I have the same car and was having the same exact problems, I replaced the AIC and it all went away. You can also check for vacuum leaks, I replaced the line going to the brake booster because it was leaking also.

Your oil pressure is probably fine, it won't be at 3 bar unless you are on the gas. It's normal to have 1-2 bar at idle. If it's bouncing at idle, just replace the sender. These M103 engines are very reliable and put out a good amount of power.

103 engine . Likely idle control valve is dirty or failing. . Erratic idle is also causing by a failing battery or a generator not maintaining correct charge condition, all the old fuses should be replaced with fresh set of copper tip ones to prevent electrical gremlins creeping in .