w124 idle (slight hesitation, lumpy) and oil pressure

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Joined
Mar 11, 2019
Messages
47
Location
London
Car
W124, W108
Hi All

I'm back with some more questions.

So when the w124 300E (m103) warms up and engine temp is between 80-100c, and i stop at traffic lights with the car still in Drive, I can feel a slight hesitation in the idle, and oil pressure drops to just under 1. If I put the car in Neutal it rises just above 1.
When accelerating the oil pressure rises to 3.

So I removed the distributor cap, and inspected it, giving it a clean with wd40, and some wire wool. Could probably do with replacing it to be honest.
Put it back, idle seems the same.
I noticed my car didn't have the round orange plate, so not sure if this could cause the idle issue ?

I took off the idle control valve, and tried to give it a clean. Not sure if this makes any difference to the idle hesitation.

Just thinking what else I could possible try apart from replacing the distributor cap and rotor arm.


Thanks
 
The distributor bodies are known for harbouring condensation. Starting from cold everything is fine but as the engine/distributor heats up the water migrates to the inside of the cap causing HT shorting- normally this causes a misfire but you might have just a little dampness in there. Cure is to give the inside of the distributor body a blast of hot air from a hairdrier for a few minutes -if your uneven idle goes away you have affected a cure for a while. -maybe thats what the orange shield is for ? to keep moisture and oil away from the inside of the cap. If you do decide to replace the cap and rotor arm don't skimp on cost-it will pay you in the long run .Some reports of poor quality after market Bosch caps- inspect carefully for manufacturing defects--Beru might be a better bet
 
Thanks Grober. Yes I will get a Bosch distributor cap and rotor arm, and i will give the hair dryer trick a go.

I have browsed many forums, typing in different search criteria, but it is always a good feeling when you get a decent reply from more experienced people.

Thanks again. Much appreciated.
 
If this W124 is old enough there will be no idle speed control. i.e. there is nothing to compensate the idle speed for the extra drag of it being in drive as opposed to neutral. The idle speed then has to be set in drive or park and will be a little too high in neutral.

The idle speed setting screw simply bleeds air around the throttle plate. I used to find it could become partially blocked with oil from the engine breather which would lower the idle speed. I used to count the number of turns until fully closed and then remove idle speed screw altogether to get access for cleaning. Also used to clean out the hoses while I was at it.
 

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