W124 E320 Irregular revving when idle

[papeter17]

Hi,

Irregular Revs at engine idle

I see someone on this forum who has similar problems with his E220! When the engine starts up the rev shoots up to 1000rpm approx and then comes back down to low revs and then appears to stall but doesn't. This also happens after the engine has run for a bit when stopping at lights for example. It doesn't make any difference if it's in neutral as the same thing happens.

I have an E320 (M) Estate and my local garage can't do a proper diagnostic check as he says I have to take it to an authorised Merc dealer who charge £80 just for a manual diagnostic check as it's an analogue test or code read which takes longer to do than a more modern car.

I've been told it could be a series of things and I have taken it to 3 garages and they say it could be head gasket as there is some slight oil leakage that appears in the oil tray! One guy suspects Air Leak/Throttle Housing fault but couldn't be sure

I am loathe to spend £80 quid just to find out that it could be some relatively simple to fix! I am not a techie so I can't fix it myself!

Anyone with suggestions I will mention it to my garage.

BTW does anyone know where can I buy a drivers wing mirror (azurite metallic blue) for this vehicle.


I would be more than grateful for any help on this!


Cheers



Peter

 

[Bolide]

Irregular idle

Peter

I think you need to search this Forum to find a local specialist. You need somewhere with a Star machine to read the fault codes and where the mechanics don't demonstrate their ignorance by plucking ideas from nowhere. Cylinder head gasket causing revs to rise at idle? I find that hard to believe

As the idle is controlled by the ecu, either the ecu has a fault or it's receiving a signal that is making it raise the idle for some reason. This could be a faulty sensor, bad or dirty AFM - there are lots of possible reasons

You just need to find someone you can trust, who is equipped & able to diagnose the fault and whose labour rate you can afford

Nick Froome
www.w124.co.uk

 

[turnipsock]

My 320CE does exactly the same.

I checked the AFM for dirt and checked for any obvious leaks a while ago but this made no difference.

I just put it down to the ECU doing it's job.

 

[w124nut]

My previous W124 (E220) did this and I took it to a local indepandant garage at Ilton in somerset. The owner there removed the car's airfilter and sprayed and cleaned out the barrel of the carb'. It worked just fine after that.

 

[popuptoaster]

dunno about mercs specifically but hunting at idle is often a sign of an air leak, if you spray WD40 all round the air hoses on the engine while its running you should get white smoke out the exhaust if any of it is being sucked in from a leak, dont do it while the exhaust is really hot though as WD40 is flammable, i have never had any probs doing this on cars.

 

[papeter17]

Thanks Guys.

I must say you have been really helpful and I thank you.
Have found a garage with bosch diagnostics
and hopefully they will sort it for me.

I will report the findings afterwards for the benefit
of those with similar problems.


Peter

 

[cubicincubi]

my 94 E280 had a irratic idle when staionary also.

it actualy tried to pull away and unless you kept your foot on the brake it would leap frog forward. New ECU did not cure this. TB was cleaned out and it was ok for about 3 days. sold it with this issue.

My current E200 idles high when in park or neutral once at operating temp. idles fine in all auto gears when stationary. on lpg and petrol.

I dont know where Idle Control Valve is situated and assume it needs cleaned.