230k M111 CLK. Poor Fuel Consumption - very bad

[tjs_riley]

Hi. I have a 2001 CLK 230k M111 Engine (owned since new) with about 100,000 miles on the clock. The cat, backbox muffler and muffler have all been changed because of wear (to original Merc parts except for the muffler which is now a Remus)

For the last 30-40,000 klicks, my fuel consumption has steadily gotten worse (and this in on a diet of Mobil 1 0W40 every 10,000 klicks and all recommended changes). I recently changed the MAF and O2 sensors as well as the one way valve to the supercharger as well as the low end breather hoses.

Still no joy. If anything the fuel consumption has gotten worse ~ 14l/100km and the low fuel light comes on at 355-360 km where when new, it would come on ~470-490 km mark (a full tank is 60 liters - the above figures are based on actual fuel consumption and not the trip computer).

On idling the computer puts the fuel consumption at ~20-26 l/100 km !

Upon starting in the morning (temp ~27 deg C), the average fuel consumption is ~17 km/100l before dropping down to ~14 after 30 km or so (and this is while feathering the accelerator)

I did a dyno last week out of curiosity , 154.4 bhp on the wheel ( which equates to 193 bhp on the flywheel ~ no degradation from original spec) and the fuel air lamda reading of 12.5 (which I'm told is a bit rich)

Does anyone have any other suggestions on what else I should be looking at ?

 

[momomo]

Does the car drive fine? Any rough idling, goes when you want it to without hesitation etc?

You seem to have changed most of the obvious and common things that cause any issues.

When was the last time plugs and air filter were changed? Also have have you checked to see if your cam sensor is ok and not leaking oil? This oil can migrate from the loom into your ECU and also foul your O2 sensors. Common issue.

When you replaced your MAF did you check the intercooler hoses from the charger to the MAF? They sometimes have oil in them if you have ever had any breather pipe issues and need to be cleaned as the oil will ruin your MAF eventually.

You mention you changed the low end breather hoses, i presume you mean the ones under the manifold?

AND finally have you had it put on STAR, to see if any fault codes are coming up?

 

[Liloff]

Quite weird to be honest.
Mine is 2.0 Kompressor 192hp. I get quite similar consumption in city. 13-14 and it starts from 30 down while feathering the pedal.
(manual gearbox)
What you could do is to clean the throttle body and the small circulation flap next to the air filter. This might have something to do with the air/fuel mixture.
... or leaking injectors.

Is your idle stable?

one way valve to the supercharger as well as the low end breather hoses.

Where are those mate?
And OFF-topic request. Would you please make a clip of the exhaust sound. I have never found a clip good enough to give me the idea of what 4cyl CLK Kompressor might sound like with a good exhaust.

 

[momomo]

YouTube - C230 Kompressor Full C36 AMG Exhaust upgrade

Use to belong to a member on here i believe.

The lower load breather system mentioned is under the intake manifold.

The one way valve is at the back of the supercharger area. Diagrams can be found on the russian website.

 

[Liloff]

Thanks, will check this out.
By the way:

and the fuel air lamda reading of 12.5 (which I'm told is a bit rich)

What would be the measurement unit for this 12.5? Would it be the Intake manifold pressure reading in Bars (or mBars)?
If yes, i consider 1250mbars quite ok.

 

[NormanC]

Thanks, will check this out.
By the way:
What would be the measurement unit for this 12.5? Would it be the Intake manifold pressure reading in Bars (or mBars)?
If yes, i consider 1250mbars quite ok.

Lambda is a ratio and so doesn't have units! Stoichiometric ratio for petrol is usually assumed around 14 so 12.5 is a bit rich.

I'm not sure how you got from 12.5 to 1250 millibars but this would indicate .25 bar boost. 1000 millibars = 1 bar which is normally considered to be a typical atmospheric pressure at sea level - just listen to the late night shipping weather forecast on Radio 4.

 

[Shude]

And OFF-topic request. Would you please make a clip of the exhaust sound. I have never found a clip good enough to give me the idea of what 4cyl CLK Kompressor might sound like with a good exhaust.

I had a C43 exhaust on my c230k and it sounded amazing! Fit was easy just needed to have a sleeve fabricated between the factory pipework and the much larger AMG backbox fitting. If anything it was almost too loud though, set off a couple of car alarms when blipping the gas pedal in a carpark and if you lifted off after a spirited drive it used to pop and bang a bit

 

[shorty]

What temo is the engine getting up to , it should be around 87 c .
I was having problems with fuel comsumption , it was a leaky stat , the car was only getting to 60 c , with a new stat the mpg has increased from 24 to 26

 

[andy27168]

Hi. I have a 2001 CLK 230k M111 Engine (owned since new) with about 100,000 miles on the clock. The cat, backbox muffler and muffler have all been changed because of wear (to original Merc parts except for the muffler which is now a Remus)

For the last 30-40,000 klicks, my fuel consumption has steadily gotten worse (and this in on a diet of Mobil 1 0W40 every 10,000 klicks and all recommended changes). I recently changed the MAF and O2 sensors as well as the one way valve to the supercharger as well as the low end breather hoses.

Still no joy. If anything the fuel consumption has gotten worse ~ 14l/100km and the low fuel light comes on at 355-360 km where when new, it would come on ~470-490 km mark (a full tank is 60 liters - the above figures are based on actual fuel consumption and not the trip computer).

On idling the computer puts the fuel consumption at ~20-26 l/100 km !

Upon starting in the morning (temp ~27 deg C), the average fuel consumption is ~17 km/100l before dropping down to ~14 after 30 km or so (and this is while feathering the accelerator)

I did a dyno last week out of curiosity , 154.4 bhp on the wheel ( which equates to 193 bhp on the flywheel ~ no degradation from original spec) and the fuel air lamda reading of 12.5 (which I'm told is a bit rich)

Does anyone have any other suggestions on what else I should be looking at ?

Hi,
You mention you have replaced the MAF and the O2 sensors, were they gen items or Bosch? as cheap items from e-bay and the like can cause issues and as it appears your running rich this might be worth considering.

 

[tjs_riley]

Thanks for taking the time reply guys !
To answer some of the questions :

1. MAF and O2 sensors were replaced by dealer. So I assume they didn't get them off eBay!

2. The 12.5 is the lambda reading from the dyno. I don't think it has anything to do with millibars. I'm told forced induction systems (kompressors and turbos) normally burn a bit richer, but is 12.5 normal or too rich?

3. The one way valve to supercharger is item 86 on this website :
http://www.detali.ru/cat/oem_mb2.asp...SGR=015&SGN=01
Gutless and misfire W208 CLK - Mercedes-Benz Owners' Forums

4. The low end breather hose and valve I mentioned changing above is the one pictured in post #15 here (to answer momomo post #2) :
http://www.mbclub.co.uk/forums/engine/81825-4-fouled-plugs-96-230-slk-advice-plz.html

5. Shorty, your post above (#8) was interesting. But what is a "stat" exactly ?

6. To answer the query about idling, its a bit strange. Sometimes the vibration coming from the exhaust is a bit rumbly, sometime smooth. Also sometimes in traffic, a quick lane change, putting boot to accelerator to overtake, results in a slight lag of a sec or two before then engine revs up and accelerates. I've been having the BAS/ABS signal light up occasionally and I think it might have to do with the steering angle sensor. Would that affect it, do you think ?

7. Oh and no faults on the Star Diagnostic.

 

[momomo]

5. Shorty, your post above (#8) was interesting. But what is a "stat" exactly ?

A thermostat.

 

[shorty]

A thermostat.

Yea the thermostat ,
i probably should of been more clear ,

 

[momomo]

Yea the thermostat ,
i probably should of been more clear ,

Dont worry, i thought it was clear

 

[tjs_riley]

OK Thermostat
How did they diagnose the faulty thermostat ? Did it show up on the Star Diagnostic?
Or did it show up on the temperature reading on the dashboard instrument cluster ?

Incidentally, the ambient temperature outside where I'm located is generally about 34-37 deg Celcius, if thats any help.

 

[momomo]

I dont think shortys thermostat was faulty as such but over time they wont work as efficiently as they should.

The combination of poor fuel consumption and the temperature of the car which wasn't even getting anywhere near 80, where normal operating temperature of the engine lies, lead shorty to replace the thermostat.

Its a cheap and easy part to replace if are thinking of doing it. What temperature does your car run at when warm?

 

[tjs_riley]

I dont think shortys thermostat was faulty as such but over time they wont work as efficiently as they should.

The combination of poor fuel consumption and the temperature of the car which wasn't even getting anywhere near 80, where normal operating temperature of the engine lies, lead shorty to replace the thermostat.

Its a cheap and easy part to replace if are thinking of doing it. What temperature does your car run at when warm?

Well from the analogue guage on the the dashboard, ~ 85-90 deg centigrade. So if accurate, running a little hot if anything.

Whereabouts is this thermostat located anyway ? In the radiator ?

 

[momomo]

At the front of the engine block, follow the pipe from the radiator.