Auto gearbox query - Mercedes W115 280CE

quenching

Any advice on what might cause the engine to sound a bit rough when a W115 280CE is in Drive but the car is stopped? All seems OK when its driving, gear changes are smooth enough but when you stop in Drive the engine revs regularly rise and fall a little, same in Reverse but not when in Park or Neutral.

Its a car I went to see today but know little of what might be the issue with the gearbox, its had a replacement reconditioned box fitted. Is it something that just needs adjusting or is it a bigger more expensive problem?

artic

quenching wrote: »

Any advice on what might cause the engine to sound a bit rough when a W115 280CE is in Drive but the car is stopped? All seems OK when its driving, gear changes are smooth enough but when you stop in Drive the engine revs regularly rise and fall a little, same in Reverse but not when in Park or Neutral.

Its a car I went to see today but know little of what might be the issue with the gearbox, its had a replacement reconditioned box fitted. Is it something that just needs adjusting or is it a bigger more expensive problem?

Its a bit hard to tell without hearing the noise, I would be intrested in the car if you are not intrested any more.If you do i would appreciate if you would pm me the details if thats the case,;)

245

My Dad's Rovers did that too - it wasn't excessive though and I always assumed that it was because the engine was slightly under load at idle from the transmission (you'll notice that the car has to be held with the brake to stop this load translating into motion).

That's my theory, for what its worth. Anything that I've ever read about troublesome auto boxes is usually about faults that are apparent when driving and clunks when selecting gears.

quenching

Will do Artic.

Don't think this is the way it should be 245, all others I've driven haven't been like this. The owner agrees its not right but doesn't know the reason, he's a nice older gent who's being very straight about any potential problems. I suspect its not expensive to fix as it drives nicely and changes smoothly.

Any auto gearbox specialists in south Dublin who know about old Mercs that I could contact?

MercMad

Its most likely that idle has been adjusted using the throttle position stop instead of the air screw.

There is a POT on the throttle flap with a micro switch and either this or the throttle lever solenoid is maladjusted. I doubt its a problem with the 'box itself.

I dont recall exactly the components on THAT car but I am sure is more likely to be a fualt in the set up than a faulty component.

quenching

MercMad wrote: »

Its most likely that idle has been adjusted using the throttle position stop instead of the air screw.

There is a POT on the throttle flap with a micro switch and either this or the throttle lever solenoid is maladjusted. I doubt its a problem with the 'box itself.

I dont recall exactly the components on THAT car but I am sure is more likely to be a fualt in the set up than a faulty component.

Thanks AGAIN MercMad, a mine of useful information! Your diagnosis seems to tally with what a Merc specialist mechanic says, so maybe this one deserves some more investigation.