A1EK

Recently my car seemed to be a little hesitant on acceleration and I found the issue was a dirty MAF and when I cleaned off the slight oil deposits on the sensor the car performed perfectly afterwards. My question is should there be an oil residue in the pipe coming from the manifold to the MAF? and if not how to avoid this?

Thanks

cindyclk

The only way you are getting oil on the MAF is from your K & N air filter...as has said so many times why not to use them.

A1EK

Im not sure what your implying, are you saying the K&N is no good and is letting oil through to the pipe, or the oil is coming off the filter?

cindyclk

It's coming right off the filter. Where else could it come from. The flow of air is through filter directly into the MAF. Just do a search and see how many people have had MAF failures using k&ns.

humbfig

I already answered your question on this thread:

https://mbworld.org/forums/clk-class...lve-reset.html

The oil comes from the engine oil vapor vents.
Every CLK has this issue sooner or later regardless using oily air filters or not.
Mercedes has redesigned some parts so it will not happen so easily.
K&N has spoken about this and "?proved?" the oil could not come from their filters (at least in some cases they are right, it could not come from their filters).
I don't use K/N or any other oily filter!

A1EK

Hmm Im not sure you are right here, as my filter is on one side of my car and the MAF is on the opposite side and the pipe comes right out of the throttle body,?

Also the oil is dark in colour not the red colour from K & N so not sure what you mean?

A1EK

Thanks have you got any pics of the venting parts that can get blocked you mentioned?

humbfig

The following thread on the british forum has some info and some nice pics on the subject. If you have the 230Komp, the upper vents, oil separator, etc.... are obvious as soon as you lift the hood and are easy for you to unclog / replace. The problem are the vents under the admission. You have to remove the admission to get to it. And then you will find some brass noozzles that are pressed into the engine. These are not easy to remove if your engine is more than 2 years old...
Good luck and don't buy a new MAF before you solve this issue.
As for the K&N you can look for info on this subject, including the K&N response. They absolutely deny the possibility of the oil being released from the filter (if it would, for sure the MAF would be in the way) and even posted some videos doing some experiments. I can't be sure they are right, but most cars (most notably compressed engines) get oil on the MAF when they age, not only CLK's, and most cars get clogged oil breathers when they age. It can't be a coincidence......

http://forums.mercedesclub.org.uk/sh...ad.php?t=33993

PS- This thread is also good reading: http://forums.mercedesclub.org.uk/sh...ad.php?t=17505

A1EK

Many thanks ! This is the most constructive answer i've seen and is exactly what my symptons are as my car has 130K miles. For those who have read comments on K&N filters not being good and discharging oil, I would say that I have seen no evidence of this and still would buy one !

humbfig

There are too many forums, it's complicated.....
Maybe a post I wrote on yet another forum on the MAF subject could be useful to help distinguishing MAF symptoms from other 100 different causes that might look like MAF problems.

http://www.benzworld.org/forums/w208...anny-prob.html

What I wrote somewhere on that thread:

Quote:
Originally Posted by bavsta
i have no check engine light on so i guess my maf is ok.

NOT!

Usually MAF problems will not signal any error. That would happen if the readings from the MAF would be way out of touch (like a broken filament). A slightly dirty MAF will not signal any error. A certain amount of air is going into the engine and the MAF will report a slightly different amount. But there's no simple way for the ECU to know this is happening. If the CLK was an airplane there would be 3 MAF's, and the ECU would signal a broken MAF when getting one reading different from the other 2.

So, how do you know it's the MAF?
On a constant throttle, or when handling it very gently, the ECU will be in a closed loop. This means it will look to the MAF readings and the oxygen sensor readings. If the MAF reports a slightly wrong value of air mass entering the engine it will be noticed by the oxygen sensor and the engine will adjust accordingly and run fine. It's a closed feedback system, and therefore can cope with small errors.
When you depress the throttle more violently, or release it, the ECU will enter an open loop. The open loop could mean different things to different cars. On the Kompressed CLK I think the open loop means the ECU will disregard the oxygen sensor and look solely to the MAF and use pre-recorded values for the ignition timing and fuel injection. Now it's the time when things go wrong, because the MAF is reporting wrong air mass values and there's no way to compensate.

So, a good indication of MAF issues is a good engine behavior on constant speed or gentle variations of speed and bad engine surges on intense throttle variations either way. No check engine lights!