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1985 om617 engine swapped 300E W124 1986
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15 Posts
Discussion Starter · #1 ·
I bought a CLK320 about a month ago and I am currently getting 4-4.5 km/l (9-10 mpg) every fill-up, after driving with feather feet. I cant even get to 250km with a full tank! MAF is new, spark plugs are new, and new coils and wires are on the way, but I honestly doubt they are the reason to my horrible fuel economy.

Something must be awfully off. I measured exhaust gasses and it turned out way too perfect...
Idle:
CO : 0.08%
HC : 100 ppm
CO2 : 19.7%
AFR: 14.7
H/C : 1.85
O/C : 0.00

3000 rpm:
CO : 0.15%
HC : 64 ppm
CO2 : 19.8%
AFR: 14.7
H/C : 1.85
O/C : 0.00

Also, my ASR/BAS light is always on, iirc it's a connection problem with the BAS ECU that's causing it, and the Check Engine Light does not work at all, yet the bulb is there. The car pulls pretty hard to the right, even though a wheel alignment was performed.

Anyone got a clue? I am going mad!
 

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Premium Member
'99 SL55 AMG & '00 CLK55 AMG
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398 Posts
Surprised indeed, from personal experience, I found the 320 to be the most economic Mercedes I ever owned
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG. 2011 BMW 335d
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6,242 Posts
Check for dragging brake calipers.
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG. 2011 BMW 335d
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6,242 Posts
Yes, if the brakes are dragging. Then the engine is fighting the brakes, hence the bad mileage.
 

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Registered
99' E320, 00' E320, 03' E320T, 05' C230K
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4,056 Posts
Dragging brakes can be check with an infrared gun. I would replace the brake hoses when you replace your pads. These cars are 20+ years old now. Lube the calipers pins with a silicone grease like Sil-Glyde.
 

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Registered
99' E320, 00' E320, 03' E320T, 05' C230K
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4,056 Posts
Yes, if the brakes are dragging. Then the engine is fighting the brakes, hence the bad mileage.
Could be the reason your car is pulling to the right also! Maybe this is causing your ASR/BAS light to come on too as a wheel is turning slower?

Depending on the year of your car, you may have to scan thru 38 pins port under hood for ASR?BAS codes.
 

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Registered
1985 om617 engine swapped 300E W124 1986
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15 Posts
Discussion Starter · #8 ·
Alright, Ill replace the hoses and pads as soon as they get delivered here.
I really hope that solves the problem because thats some really mysterious stuff right there.
 

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Registered
2002 Mercedes CLK320 Convertible W208
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10 Posts
Alright, Ill replace the hoses and pads as soon as they get delivered here.
I really hope that solves the problem because thats some really mysterious stuff right there.
Hi, Dragging brakes could be a cause and would explain the thin pads and poor consumption but that would be the result of a frozen/stuck calliper. So when you do the pads take the callipers off and give then a good clean with brake cleaner and then grease the moving parts with high temp brake grease (not copper). They should slide easily. The pressure cylinder should slide back into the calliper with the use of a clamp. Check the rotors too for deep wear or scorching, they may need to be replaced. I did mine recently and it was not a big job and, come to think of it my consumption improved a bit too.

Replacing the brake hose on this age vehicle is a good idea but I doubt it will fix your issues.

Also, if the engine is just guzzling petrol I would expect it is running rich (but your numbers look OK, I think). A simple way to check this is to go to the back of the running car and snatch a handful of exhaust up to your nose. If it smell of petrol your rich. If that is the case you should look at the O2 sensor. Might be sending false signals to the ECU.

My workshop manual lists:
  1. dirty filter element
  2. low tire pressure
  3. binding brakes
  4. leaking fuel
  5. dirty fuel injectors
  6. ECU malfunction
  7. thermostat stuck open or missing
  8. Transmission faults
There is also something called "inlet manifold tuning" (?) arms that can break, jam or just stop working. I don't know much about them but they are at the back of the motor near the heads. If all else fails, something more for you to research :(.

That is probably more than you needed. Hope you find the cause.
 
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