Revs Rocking

[*BigMac*]

Another problem has arrived with my 1999 C250TD W202T

When driving and staying at a steady speed – be it 30mph 50mph or 70mph, doesn’t matter what speed I’m sat it, I get a dipping in revs then it goes back up again – this is constant, thus giving a backward and forwards rocking motion that only stops if I accelerate or decelerate and then comes back once sat at a constant speed its back.

Any ideas what might be causing this

 

[*BigMac*]

Any thoughts????

 

[*BigMac*]

Please???????

 

[JEZ.S320L]

Please???????

Not heard of THAT before Be patient - someone will be along soon to advise.

 

[Aussie Nick]

Do you mean that it occurs only when the cruise control is engaged?

 

[*BigMac*]

Do you mean that it occurs only when the cruise control is engaged?

No fella, it’s when you sit at any steady speed - say your off to Tesco and following the flow of traffic and sat at a steady 30 then the revs drop and rise, or sat on the motorway at a steady speed, again the revs drop and rise, I’ve not tried it with the cruise on, to see if it still does it.
The revs drop and rise no matter what speed you sit at, as long as you’re just driving along normal, and not braking, accelerating or lifting off
Question
If the gearbox oil was low or contaminated that wouldn’t do it would it????, going to do a oil change on the box soon as I can’t see it ever been done on the service history, and the cars done 74000 miles now so must be about due it anyway


cheers Steve

 

[BlackC55]

Some kind of air leak maybe?
That is a tricky one.

 

[*BigMac*]

That is a tricky one.

Indeed - Looks like I might be taking a trip to Dronsfield

 

[Bolide]

Disconnect the vacuum pipe to the EGR and see what happens

Nick Froome
www.w124.co.uk

 

[*BigMac*]

Disconnect the vacuum pipe to the EGR and see what happens

Nick Froome
www.w124.co.uk

Sorry can you elaborate, What will that show / not show???