w134 e220 1995 MAF problem HELP

[ross255]

Hi,

I hope you can give me some advice.

I have a 1995 w124 E220.

recently the mpg has been getting worse and worse.
The most i can get is 17 mpg. it used to be a regular 25 to 30. so i know i am not imagining things.

any way, in an effort to find a fault, I think i have narrowed it down to the maf.

This is because, whether it is plugged in or not the car drives the same.
So i a guessing that the car is running in a diagnostic type mode and is ignoring the maf, and using lots of petrol.
Am I guessing right? after all shouldnt there be a noticable difference between having the maf plugged in or not?

hope you can help.

 

[television]

Hi,

I hope you can give me some advice.

I have a 1995 w124 E220.

recently the mpg has been getting worse and worse.
The most i can get is 17 mpg. it used to be a regular 25 to 30. so i know i am not imagining things.

any way, in an effort to find a fault, I think i have narrowed it down to the maf.

This is because, whether it is plugged in or not the car drives the same.
So i a guessing that the car is running in a diagnostic type mode and is ignoring the maf, and using lots of petrol.
Am I guessing right? after all shouldnt there be a noticable difference between having the maf plugged in or not?

hope you can help.

Welcome to the forum, and yes it would appear that it is not working, this being the case it would stay at the cold settings making the car thirsty. It could be one of the sensors but this is rare

Buy one from Bosch as the are much cheaper

 

[ross255]

Hi,
thanks for that, i have ordered a new one.
It actually been a very reliable car, and before me,was owned by my father from new.
I am just glad it shold be a simple fix.

 

[television]

Hi,
thanks for that, i have ordered a new one.
It actually been a very reliable car, and before me,was owned by my father from new.
I am just glad it shold be a simple fix.

When you get the new it should go back to normal after a short drive, if it does not, it will just be a faulty air or temp sensor. Good luck

 

[ross255]

Ok, after instaling a new MAF the mpg have improved to more or less what it should be.

However, I still have an eratic idle from 600 to 1000 rpm.
It used to idle faultlessly at 550 rpm.

It also sometimes stalls when the aircon comes on, or revs shot up to 2000rpm when just starting to pull off.

Which leads me to think the throttle sensor/ switch and idle motor may be faulty. Does anyone know how to test/clean them.

The merc system is a bit odd, as it al seems to be part of the throttle body. I am used to older bosch systems that have seperate throttle switches and idle motors.

So any help would be great.

ps. is a w124, but i cant edit the title to correct my typo

 

[television]

If yours is a 124 with Motronic then check the idle switch that plugs into the airflow sensor, unplug the lead,start the engine where it should be on high idle, the short the two wires out in the plug on the lead, if the revs drop to normal it is the inbuilt switch

 

[ross255]

Hi,
Where is the idle switch supposed to be? the only other thing that I think controls the idle looks like part of the throttle valve, and it does have wires going to it.
I am going to have a look right now.

By the way its the 2.2 16v, so i assume its motronic (i think it may be refered to as the HFM?)

 

[ross255]

Ok, I have found the idle switch on the throtle body, it still clicks when i start to move the throttle by hand.
However, the wires go into another part of the throttle body which has a black cover, and i think controls the cold start idle speed.
The wires from that then go to a plug under the intake manifold which has 8 pins.

I am now stumped as i cant tell which wires to test, is it worth taking it off and taking the idle part of it apart and cleaing it, is that possible.

 

[television]

Item 152 is the idle switch there are only two wires, if you short them out it would confirm the switch

http://www.detali.ru/cat/oem_mb2.as...GM=717.413&CT=F&cat=15T&SID=54&SGR=120&SGN=06

 

[ross255]

The pictures not very clear, but I think it is on the throttle body, and the switch is closed by the throttle cam.

Itdoes not go to two wires on my model, it is all part of the throttle body and hs a 8 wire plug.

 

[television]

The pictures not very clear, but I think it is on the throttle body, and the switch is closed by the throttle cam.

Itdoes not go to two wires on my model, it is all part of the throttle body and hs a 8 wire plug.

Sorry that leaves me out for the minute,I have ny MB computer down at present

 

[television]

Maybe you could find something on Benzworld

 

[ross255]

Just looking on benzworld, never knew that it existed.

I have found similar problems where people have had to replace the throttle body, but its an expensive part to change without being 100% certain.
Plus I always like to try and fix before replace.

 

[C220GJS]

You could take the black cover off the idle contol motor and check that there things have not corroded. I have read of problems here that have been cured by lubricating the motor and gears. Security bit required to remove cover.

 

[television]

As George above, where the carbon track has worn, it is possible to alter the wiper so that it tracks on a different part of the track

 

[ross255]

television,

I think you are on the right track (excuse the pun)
I have cleaned the thottle, the stop switch works, but just off idle the thing goes bit nuts, trying to rev but not able to etc. I am aware of the carbon track trick, and have done it on another cars airflow meter.

I have taken the back off the throttle/idle control motor, nothing corroded where the gears are.

The carbon track looks as if it part of an enclosed white case, does anyone have any pictures or a "how to" guide, before I start working blind.

Your help is very much appreciated, as taking a car of this age to a garage just does not make sense.

Update: I have the thing backoff, but to get to the carbon track, it looks as if i have to take the throttle butterfly ad spindle out. From what I can see it appears welded on both end (no nuts just flush metal) So I am stuck.

 

[television]

Do you have a carbon brush on the wiper

 

[ross255]

the carbon brush and track is encased in a white disk around the throttle spindle in the idle control valve part of the throtle housing.

 

[television]

I do have some details somewhere, but I am running a re booted PC and not easy to find the info on this.

While I am looking there is one USA site that gives the info on how to fix, I beleive it is a matter of making a new brush that uses an unused part of the track , its one of the re building sites that gives this info

 

[ross255]

I am having trouble finding any info.

From what I can see, to get to the track and wiper/brush I will need to dremel the cover off it.

Update: I have dremeled the cover off. It is just that, a cover.
Underneath are two sets of brushes running on tracks. One for the whole of the throttle movement, the other for the moverment required for idle.
I cannot see any easy way of movng them, the best I can probaley do is clean them.