2000 430clk.
Got CEL P0170 and P0173. Likely suspect is the MAF. MB provided the following test. Place car in 3rd gear. Accelerate at WOT and record the MAF when engine hits 4000 RPM. For this car the MAF should show somewhere around 525kg/hr (from memory, don't remember exact figure). I measured 400kg/hr. car lacks power at WOT. Will replace the MAF because it failed the test. Idle is perfect (smooth) so vacuum leak is unlikely.

Before deciding to replace the MAF always try disconnecting and reconnecting the MAf (with engine off). Sometimes the contacts develop an oxidation layer that falses the readings. Reconnecting can "clean" the contacts. In my case it made no difference and I still read about 400kg/hr.

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1972 450SL
1982 300D Turbo

Try cleaning it . . check out MENU#4a . .

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Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

....and check your air filter. too.

Air filter is new. Cleaning the MAF is a good idea but I've heard that the problem usually comes back if only a cleaning is done. I'm doing this for someone and don't want them coming back in a few weeks with same complaint. Have you had experience with cleaning and lasting results. Do you clean with aerosol, such as brake cleaner or do you use a swab and alcohol?

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1972 450SL
1982 300D Turbo

I use CRC MAF cleaner ..aerosol.
Works great and fast/easy to use..

I cleaned the MAF with CRC electrical contact cleaner which is the same formulation as CRC's MAF cleaner. Results were negative. I then tried cleaning it with alcohol on a swab and got modest to no improvement. I replaced the MAF with a new Bosch unit and car is fixed! I'm measuring about 550kg/hr at 4000 RPM, 3rd gear WOT. This is what it should be.

btw, I've "fixed" a few Toyotas throwing lean codes by spraying the MAF but doesn't seem to work as well with these MB Bosch film type MAFs, at least in my limited sample group.

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1972 450SL
1982 300D Turbo