W202 with a mind of its own.Help

[rhino8572]

I'm trying to find out if I have a big bill looming and hope someone can tell me I can cure this myself.

Over the past couple of weeks / a month I have noticed that when I come to a stop at traffic lights or I am in neutral the rev counter fluctuates between 500 - 1500 revs. It does not do this all the time, but when it does the auto gear change is also very erratic, I am sometimes at 4,000 revs before it decides to change up.

I have cleaned the MAF (new in Oct), changed the battery and put a new air filter in but noticed very little difference, I've also over the past couple of days noticed a smell of petrol which makes me think I'm running rich, as I am not loosing petrol but fuel economy is not great.

Can anyone help.

 

[Parrot of Doom]

Need more information on the car - petrol, diesel, engine size etc.

 

[rhino8572]

Sorry, its a 1997 C200, auto, W202, petrol.

Thanks

 

[C220GJS]

If you smell petrol from the exhaust, you may have a failed Lambda sensor, take it to an MOT station and ask them to check the emissions.
If you allow it continue to overfuel it will burn out the catalytic condenser.

 

[type49]

Might be worth cleaning out your throttle butterfly. At least it won't cost you anything.

 

[JohnnyW]

Similar problem......possibly!

Hi,

What is the throttle butterfly and how do you clean it?

Johnny

 

[C220GJS]

Have a look at this diagram;http://www.detali.ru/cat/oem_mb2.as....418&VIN=*&CT=M&cat=19K&SID=07&SGR=040&SGN=01
;the throttle butterfly is the flap inside the idle speed actuator which controls the airflow.
Clean out all the accumulated gum using carb cleaner or similar solvent, then lubricate all the linkages.