Clean the MAF and sensor
MAF DIY PICTORIAL: replacing/cleaning - Mercedes-Benz Forum
click on PDF. Also reboot the ECU
How does it run? Does it make good power? How many miles on the car?
I am surprised Jeff hasn't already offered the following....,,
Go inside, look in the bathroom mirror, catch a glance of the person in the mirror. Do they have a big grin? If so, problem found.
Look out the window, are there mountains visible? .....
Are the signs you see in German, ( possible Autobahnitis).
If no to all these you've rule out driver and environment, must be the car........
Another quick one to check not mentioned by others is a fractured cat matrix that can cause restriction.
With fuel consuption as bad as you have, there must be clear cause.
By the way,
I did a 200km freeway run, top up at 110 kph, in my 230k R170 for 8 L/100km consumption, ( about 35.3 mpg uk) ,
and came back the same 200km top down , side windows down too, for 8.5. L/100 km, 33mpg uk,
Both ways were light traffic, on cruise control, light winds.
So the high drag configuration only costs about 6% extra at highway speeds.
I am pretty happy with that.
So how did your drive for Christmas work out????????
Sorry for the delay in replying to you guys! Unfortunately, I have M.E. which I have been dealing with for over four years now. Severe Fatigue, Leg pain, nerve pain and many other symptoms can make it hard for me to reply, or do the vehicle mechanics/suggestions quickly.
However, after recovering from a 500 mile round trip over Christmas to see family. Happy Christmas!!! to you all
I gave the Additive fuel cleaner a real chance to work and filled up with super unleaded fuel. But no joy with that. Yet, I did a thorough check of looking for fuel leaks under the car, and found none. What I did find! was at 4000rpm there starts a Bang Bang Bang noise from the engine, and a unusual rocking of the actual engine itself, plus the odd pop out of the exhaust, and a subtle ping ping noise out of the engine on idle. The Banging noise was achieved in revving from Neutral only.
The performance is still great on a run (apart from the MPG which was better Long Distance at 25 MPG, but not what it ought to be) the engine is still strong when power is required. You would never know that there was an issue when driving other than the very poor MPG.
I have run a diagnostic on the car with a SLK specific diagnostic tool (Icarsoft) prior to the long distance drive when I discovered a cylinder issue on 2 saying that there was a lead/coil issue, but nothing to trip a Misfire Fault Code.
I will next run the Diagnostics again to see if after the long run it comes back with the same cylinder 2 fault.
From there, as I suspect the MAF to be OK due to great vehicle performance including plenty of power left under labor. I will start the engine under the cover of darkness to see if there are any sparks from any of the cylinders to lead us to plugs or and coils.
If, all is well there....... I am thinking that I is possible cylinder 2 could have a stuck injector needing either tapping to loosen and then another Additive treatment or sending off to get properly restored.
What do you think about this plan of action Guys?
Thank you all for your help and suggestions, I hope I have covered them all for now.