Engine missing

[Dieselman]

Ok, so at least that's working then. I still think it could be the temp sensor but don't have the resistance values.

In reality there is only the Temp sensor and Lambda left.

 

[gina2201]

Are these difficult (or expensive) to change?

 

[Dieselman]

About £25 and £50 each and easy to change, but it probably is worth getting it checked first before just changing bits until it's fixed..

 

[Dieselman]

Just to make sure of the MAS can you re run the check but when driving either a long road or up hill. We need the maximum reading the MAS can output at full throttle and max revs, say 6000rpm.

Run a wire into the car and have a passenger read the meter. Trap the wire under the MAS connector and then connect the meter probes with terminal block.

It could be that the MAS can't output enough when the throttle is suddenly opened so causes the mixture to go lean.

If the MAS can output ~4.5v then I would say it is definitely good, normally when failing they struggle to reach 4v or even lower, some as low as 3.2v.
Next stop would be the temp sensor and Lambda.

The ECU inputs are water temp, air temp, MAS, Lambda and throttle position. From those inputs it calculates airflow and engine load, so fuels accordingly.

 

[Adam230K]

Its definately not the temperature sensor as this was faulty on mine for a good 3 months and my car didnt behave like that at all.

Its £13 from MB, and it only improves the driveability if its cold or hot (hardly noticeable).

If i was you i'd get the engine checked over...

 

[Dieselman]

I think you have the same fault as this thread. It would be worth checking the voltage from the Lambda sensor.

http://www.mbclub.co.uk/forums/engine/69205-w124-m104-code-11-o2-sensor.html

The wire colours are likely to be 2*white for the heater, 1*black for the signal, 1*grey for the Gnd.

Just probe the signal wire with the engine running. A very low reading is likely to be a duff sensor.
It should switch at 1 sec intervals between 0.2 and 0.8v once a second. If the meter is slow to react look for an average of 0.45v, which is perfect mixture.

Alternate colour codes could be 1* blue = signal, 1* white = Gnd, 2* black = heater.

 

[gina2201]

I think you have the same fault as this thread. It would be worth checking the voltage from the Lambda sensor.

http://www.mbclub.co.uk/forums/engine/69205-w124-m104-code-11-o2-sensor.html

The wire colours are likely to be 2*white for the heater, 1*black for the signal, 1*grey for the Gnd.

Just probe the signal wire with the engine running. A very low reading is likely to be a duff sensor.
It should switch at 1 sec intervals between 0.2 and 0.8v once a second. If the meter is slow to react look for an average of 0.45v, which is perfect mixture.

Alternate colour codes could be 1* blue = signal, 1* white = Gnd, 2* black = heater.

After reading the other thread and the symptoms it does sound pretty familiar! Going to give it a try today and see what it comes back with.

Thanks for the ongoing advice!

 

[vijilants]

After reading the other thread and the symptoms it does sound pretty familiar! Going to give it a try today and see what it comes back with.

Thanks for the ongoing advice!

Your Lambda connector is the circular connector just above your brake fluid resevoir and if you do need a replacement, Euro care parts do the bosch one for your car, delivered for £50 off the website( Their website price is £13 cheaper than in their shops.) They are the cheapest for the Bosch one which is OEM.

 

[gina2201]

I take it this is the tubular thing with wires coming out both ends?

Can I take the readings from one of these wires then I take it?

 

[vijilants]

I take it this is the tubular thing with wires coming out both ends?

Can I take the readings from one of these wires then I take it?

Correct....if you trace one end of it, it goes to the probe which sits on the exhaust maifold. You can see the probe at the baulkhead end if the manifold.

 

[Dieselman]

The wire should be black. Check the resistance of the heater wires and that the Gnd wire has good continuity first.

Use a pin, paperclip or thin wire to get into the connector. It will be best to go for a drive to get a good average reading.

If the Lambda test is inconclusive perform the driving test on the MAS to obtain the highest reading it can give.

 

[gina2201]

Just been out to the car and disconnected this 'connector.' Took a reading from the black wire and car at idle. Reading stayed at .84/0.85v pretty much.
However after reading the last couple posts would I have to be driving the car and also the connector to be plugged in to get the correct readings?

 

[Dieselman]

Certainly connected. Driving will give a better average reading than just at idle. Look for any conditions where the voltage either dips or rises.

You've effectively just made an Air Fuel Ratio gauge. (AFR)

But don't tell anyone though..

 

[gina2201]

Certainly connected. Driving will give a better average reading than just at idle. Look for any conditions where the voltage either dips or rises.

You've effectively just made an Air Fuel Ratio gauge. (AFR)

But don't tell anyone though..

Sounds impressive!

Might have to give this a go tomorrow now, I fell asleep! You make it sound so simple, it can't be!

So I need to run a wire from the lambda sensor which is located on manifold/exhaust ? or from the connector near my brake fluid reservoir into my car and go for a drive and what should I be looking for at which speed/revs etc?

What kind of wire can I use, can't think of anything we have lying around at the mo, any suggestions?

 

[Dieselman]

Any small gauge wire will do, if you haven't got any get some cheap bell wire from B&Q, just make sure you can tell the two leads apart by marking one.

When running the reading should keep switching between 0.2v and 0.8v once a second, or if the meter is slow to react will give an average reading of about 0.5v.
If the sensor is duff it will read at the low end of the readings continuously.

Cars are simple..

 

[vijilants]

Sounds impressive!


So I need to run a wire from the lambda sensor which is located on manifold/exhaust ? or from the connector near my brake fluid reservoir into my car and go for a drive and what should I be looking for at which speed/revs etc?

One end of that connector goes to the Lambda probe and the other end goes to the ECU, so somehow get the wire you are going to connect and either poke it into the connector or use a pin and tap into the wire (carefully).

 

[gina2201]

Ok, so I wired up the car and went for a drive today....

The voltage fluctuated regularly from high to low but not within the 0.2v and 0.8v guide. I had readings ranging from 0.1v all the way to 1.7v. I did notice when I put my foot down it went below 0.2v.

Does this suggest a faulty lambda sensor?

 

[Dieselman]

The 1.7v is strange and is probably just the meter overcompensating as the voltage fluctuates.
When driving steadily and or idling what were the readings.?

If the readings were steady alternating between 0.2v and 0.8v when idling or driving steadily I'd say the sensor is ok, but if not then it's duff.

The very low reading when accelerating suggests the mixture is going lean, which does fit with the misfire.

 

[gina2201]

The readings at idle were at 0.84v.
At steady driving the figures ranged from 0.3 to 0.5v/0.8 and over 1.0v (up to 1.7v)
When under harder acceleration went below 0.2v

 

[Dieselman]

It should never go over 0.9v and your idle reading looks a little suspect. Can you just check the meter to make sure it doesn't have the battery warning icon displayed as that will skew the readings.

The very low reading seems to suggest a lean mixture on acceleration, which will cause stumbling.

It might be worth checking again once the meter is confirmed accurate then check the MAS again, when driving.

If the meter is over-reading it makes your MAS readings very suspect, which would fit with the lean mixture under acceleration as depicted by the Lambda readings.