Erratic Idling on E200 W124 1995 After battery replacement

[E200_Owner]

I have just become a owner of a 1995 E200 and because the battery was week I had the battery replaced on my E200 W124 series and suddenly the idling has become erratic.

I was told by a independent Merc garage that this was a common problem on this model and the fix is to replace the Throttle control unit which is about £300.

Can anyone advice on why changing the battery should cause this problem and if there is a way to fix the reset the electronics instead of replacing the complete unit.

It is bizzarre!

Thanks,
Mike

 

[andy_k]

our W124 developed an erratic idle during the summer, try cleaning the throttle linkage - this has worked for others but had no effect on ours

What did woirk however was to take the car for a "spirited drive" aka the "italian service" - 100 miles of motorway later and the idle problem was cured

Andy K

 

[Peter 300TE]

Although I cannot speak for MB's. On many vehicles with electronic units if the battery is left for disconnected for a period of time the units need to reset themselves this can take a few miles.

We had this problem every time a vehicle was serviced at work. A good run and it evened out.

 

[mjtray]

In addition to what Andy K said, also put some Wynns injector cleaner in the tank when you fill up next.

Then give it a good thrashing to clear the injectors.

If your car has previously had a quiet life trundling around town, its likely that the injectors will be pretty gummed up and could be causing the idle to flutter.

Do the cheap things first before you start splashing out on expensive replacement parts.

Good luck and hope it works.

ps: try and put some Shell Optimax in the next time and see if it makes a difference. I have noticed that my car hates Supermarket fuel !!

 

[pentoman]

Give us more information, what do you mean by erratic idling?

Have you at any time tried to jump start the car while the battery was flat?

If so, the OVP (Overvoltage protection) fuse (on top of the OVP relay) has probably blown, providing yours is an old enough model to have one.

99% of the time, the thing that links battery issues and erratic idling (assuming you mean stumbling and occasional stalling) is a blown OVP fuse.

Do a search to find how to find it, and test it, or search www.mercedesshop.com if you can't find it here.

 

[dieselman]

I agree with pentoman. OVP fuse.

 

[E200_Owner]

What I mean by erratic idling is, with the car stand still and engine switched on an idling the RPM keeps on changing to 2500RPM without any input of the accelerator, it will even go down to normal about 800RPM and it will rise to 1500RPM all by it self and it will keep on doing this.

If you rev the engine and let go it will still not settle down to normal it will remain where it was last.

If you flick the EC switch to start the air conditioning compressor when the clutch if the compressor will try to engage it will almost stall the engine.

Before replacing the battery the idling was very smooth and perfect the engine speed would rise and fall as the a/c compressor would engage and disengage.

I hope this helps

Thanks,
Mike