Uneven Idle - CDi C220 W203 53 Plate

salmanhamid

Senior Member
Hi All

I may sound like a broken record about the uneven idle problem I have on C220 53 Plate, again to start with.

The problem occurred when Merc (Main dealer) replaced some fuel pipes in my car after I was having a diesel smell in the car.

And Since that day I am having a uneven idle, the RPM hand basically goes down not up in my case and the even the lights flicker as well when the RPM goes down feels like it it goes to cut the engine off.

I went to a Merc Specialist, he ran a star diagnostic and nothing came up, few gentleman suggested here on forums it could be vac pipe, but its checked and its fine.

So guys any suggestions?

Naturally I have spoken to Merc and complaint that they have caused this problem because the the minute I took the car from garage I have this problem but they simply refused.

Thanks in advance guys for any suggestions.

SAlman
 
C

Chopper

Guest
Hello ,I have same problem with same engine .Mine dosnt give trouble in warmer temps for example during summer .Once winter hits I have the same problem every year. I cleaned the pipes leading to EGR which gunks up every 20k or so and this seemed to help .However Im not sure if this is the root problem !:roll:
 

BlackC55

Senior Member
I would be looking at a possible injector problem.

The values need to be checked with a Star and a leak off check done.
 

meatballs

Senior Member
If your car is fitted with the heater booster (electric type), turn this off while you are experiencing the eneven idle.With it switched off my w203 c220 cdi ticks over fine.If it's switched on or switched to automatic, it will tick over uneven.This only applies in cold outside temps when the coolant temp is below 70 deg c .
 

meatballs

Senior Member
To switch the booster off you have to use the steering wheel controls.Once you've found 'Heating' scroll down to 'Booster'.You will have 3 choices ;
1 - Switch off
2 - On EC only
3 - Automatic
If you don't have the booster on it will take longer for the heater to blow hot air.
All the above is from memory but should be right.
 
C

Chopper

Guest
took mine to MB today ,pulley/clutch assembly on alternator was seized. Got new one and fitted new belt when at it .135 pounds and running sweet again !
 

Silver_Star

Senior Member
If your car is fitted with the heater booster (electric type), turn this off while you are experiencing the eneven idle.With it switched off my w203 c220 cdi ticks over fine.If it's switched on or switched to automatic, it will tick over uneven.This only applies in cold outside temps when the coolant temp is below 70 deg c .

Thanks for that meatballs! It sorted out my problem. I think I turned mine to automatic in the summer and everything was fine untill the temps dropped, I noticed an iratic idle untill the car was up to temp. - I diddn't put the two together. It saved me the hassle of having a leak off test done on my injectors! The car wouldn't stall just every 5 or so seconds when the car was at idle or stationary in drive the revs would just drop 200rpm or so then go back to idle, never enough to cut it out just annoying.
 
OP
S

salmanhamid

Senior Member
Thanks a million Meanballs!!! I have switched the heater boster off and since that day my idle is rock solid, I cant thank you enough!!

But guys what do you think is the reason behind it?
 

mercdriver25

Active Senior Members
Could it be the MAF sensor? Worth disconnecting it to see if that helps. I had a similar prob some time ago, and after replacing the MAF, all was fine..
 

meatballs

Senior Member
Glad you all got sorted !
I think the uneven idle whilst using the electric heater booster is just down to enormous amount of current needed to to power it.I think it's a bit like turning the lights,heated rear screen and anything else electrical on at the same time,it lowers the tickover slightly.I assume that the heater booster element is being switched on and off as it heats the water around it.Only my guess though.
 

maxjazz

Member
Thanks Meatballs. this puzzled me all winter last year. Turned it off today and tickover is as steady as can be. :D
 
Top