W124 E220 surging at idle

[CRJ343]

I have an occasional surging problem with my E220 Cabriolet. It doesn't happen consistently but can be quite alarming.
It occurs in the following circumstances :-

a) When the car is warmed up and idling in traffic in "D".
b) After engaging "R", again when the car is warmed up

In both cases idling momentarily increases to about 1200-1500 rpm

The HFM air sensor has been replaaced

Does anyone have any idea what could be causing this ?

 

[e220-cab]

surging at idle

I had this prob it turned out to be the fuel tank vacume sensor thing-a-me-gig about £50 its located on the n/s inner wing i think.

 

[e220-cab]

? surging

I think its a purge valve, hope this helps.

 

[grober]

I had this prob it turned out to be the fuel tank vacume sensor thing-a-me-gig about £50 its located on the n/s inner wing i think.

E220-CAB is referring to the evaporative control charcoal filter which acts to absorb petrol fumes from the tank while the car is stationary. When the engine is running the engine ECU opens a valve at certain times to allow the engine inlet manifold vacuum to evacuate/regenerate the filter. Any leaks/problems in the associated pipework or the valve can cause weird idle problems. I my experience very few Mercedes dealers bother to change them. I am not certain this is the cause of your problem but another could be the the butterfly throttle plate sticking in its throat, which tends to get dirty over time. It s easily cleaned with a suitable solvent such as carb cleaner. Numerous posts about this if you do a search.

 

[the1beard]

Hi all

I'm having this surging problem on my e220 saloon 1994 car w124.

I've cleaned the throttle body with carb cleaner not sure if I did it correctly

Anyone know if my car has a purge valve what it looks like and where it might be?

 

[grober]

The purge valve is a small black plastic device mounted on the inner wing in front of the nearside suspension tower It will have an electrical connection going to it and 2 x 8mm black plastic tubes connected to it by short rubber pipes. one leads from the underside of the inlet manifold the other leads to the charcoal canister under the wing.

 

[the1beard]

There doesn't appear to be an complete guide to w124 idle problems and fixes on the forum.

Having read a number of posts it appears the following could be the cause of idle surge on my 1994 e220 / 220e w124

1 Air mass sensor
2 Air intake temp sensor
3 Fuel system Coolant temp sensor (not the temp guage sender)
4 Throttle body ( the one which is cleaned with carb cleaner)
5 Purge valve

As I don't want to replace all these items even one at a time until i solve the problem.
Is there anything I have missed and does anyone have any information on testing the items in the list?

 

[grober]

Just block off the purge valve line to the manifold will test that aspect. Don't block the valve itself --just the line. If you have cleaned the throttle body next stop would be the MAS/MAF then the coolant temp sensor. here's a pic- block the tube on the left of the picture and check there are no leaks on those flexible rubber connectors as they tend to perish or split.

 

[the1beard]

Just for info here is an image of the purge valve.

 

[the1beard]

Just block off the purge valve line to the manifold will test that aspect. Don't block the valve itself --just the line. If you have cleaned the throttle body next stop would be the MAS/MAF then the coolant temp sensor.

Is this the MAS/MAF ?



This is the Air temp sensor

 

[grober]

You got in there before me. Yes that's the MAFF some people clean them with solvent which can effect a temporary solution. If you do decide to replace it just get the sensor insert from pierburg or bosch--cheaper than the whole unit- don't be tempted by the cheap ones on ebay unless you are 100% sure they are a reputable source. Yes thats the air temp sensor but unlikely to have caused your problems.

 

[the1beard]

Changed the purge valve and still surges.

Looks like the MAFF next £88 for a bosch.

 

[PhantomLord]

- It could still be purge valve related, to test purge valve just disconnecting the connection at throttle body and sealing it(temporarily) should do. In my case pipe from canister to purge valve had a leak.

- It could be vacuum leak also, either the small pipes going to FPR, A/C or the break boost pipe(Usually leaks at the the one-way valve, noticeable by occasional break pedal hardness).

 

[callingdx]

I had a similar problem on my previous E220, it turned out to be the Lambda Sensor, cost about £68 for the correctly numbered Bosch replacement from a motor factor - worked a treat and a dead easy job.
Had to buy the lambda removal socket though .......£7.... ouch !

Good luck

 

[the1beard]

Today

Cleaned the throttle valve with carb cleaner again this time used a whole load more cleaner.
Also using Electrical contact cleaner I cleaned the MAFF.

And so far so good.

I've read elsewhere that cleaning can work for a while then the problem comes back a week or so later so new MAFF quite possible.

I'm going to check the error codes when I get a minute.

 

[CRJ343]

Error Codes

How do I check the error codes on an E220 ?

 

[the1beard]

Hi CRJ343

I didn't need to as my surging problem has not returned.

If you do a search you'll find posts explaining the procedure but I think it's probably a lot less hassle to go to a local specialist or main dealer and pay the £50 to get the error codes read.

Good luck

 

[Creaky]

Hi CRJ343

I didn't need to as my surging problem has not returned.

If you do a search you'll find posts explaining the procedure but I think it's probably a lot less hassle to go to a local specialist or main dealer and pay the £50 to get the error codes read.

Good luck

Hi,
I am facing an idle problem on my E220. Was wondering if your problem ever came back after cleaning the MAF. Or did cleaning it resolve the issue?
My local Merc dealership is suggesting its an electrical harness problem.

 

[coupe addict]

The harness has one very specific problem issue, which is quite easy to check and to deal with.
At the drivers side rear of the engine, the MAF wiring is clipped to a very hot spot on the engine, which can cause premature degradation of the insulation locally. Split the outer sheath carefully with a blade: if the problem is present it will show as crumbly or split inner insulation, easily fixed. If its not that, I'd look next at plugs and connectors (again easy to check/remedy) before messing with the more expensive MAF.

 

[Tel R]

Surging Sorted

On my E220 Coupe it was a broken throttle return spring.
The surging was very ackward when stopped in traffic with the auto gearbox wanting to move me on and me holding the car back on the brake pedal.