SLK320 MAF - P0170 / P0173 Codes

[lcdial]

Hello, I have a 2001 SLK320 with a check engine light - diagnosed to be P0170 and P0173 (Fuel Trim Malfunction Banks 1 and 2). From reading very helpful posts on this forum, it seems likely that the culprit is a bad/dirty mass air flow sensor. I have read about people successfully cleaning them, and as they are fairly expensive ($300 or so new for the Bosch verson), I would like to try cleaining it not only to save money, but to test my mechanical mettle. I was planning to take it out and use the CRC Mass Airflow Cleaner available for about $6 per can to clean it and then put it back (the result being a clear CEL and 10,000 extra horsepower, of course). It seemed so easy! However, after opening the hood and being confronted with the realty of actually engaging on this project, I stalled. Even though I searched these forums to find out where the MAF is (on the 320 it's at the back of the engine at the top, right?) and spotting it (I think), after opening the hood, I realized I don't even know how to get the engine cover off. In order to preserve a little dignity, I cleaned the engine cover and pretended that was what I wanted to do. So, I have a few questions: 1) Does anyone have (or know where to find) a step-by-step on getting to the MAF (out from under my now-clean engine cover), pulling it out, cleaning it, and putting back? 2) Will I need any special tools? I have screwdrivers and a sledgehammer (but I hope it won't come to that). Any help/words of encouragement would be greatly appreciated! Thanks in advance!

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[contractsguy]

I have a 230 vs a 320 so I can't offer you specific technical advice.

For the 230 the removal was quite easy; a screw driver and a pair of lock-grip plyers.

If noone else responds to you suggest you subscribe to ALLDATA, an online service manual. The data is not GREAT, but it will assist you in completing projects such as a MAF cleaning.

Hope this helps.

Contractsguy

[lcdial]

Thanks! I'll definitely check out that list.

By way of update, I think I may be a genius. As it turns out, I didn't need to clean the MAF sensor at all!!! All the car needed was for me to dust off the engine cover (as described above), and VOILA! no more check engine light!

The car has more horsepower now too. . . and it flies.

[RobertG]

To locate your MAF first find the air cleaner box and then follow the air pipe and it will lead you to the MAF which is the next part inline before the engine.On one side of the sensor it will have a hose clamp and the other will have clips
I strongly recomend getting a replacement MAF before you start your project.

[contractsguy]

Icdial,

If the light went off, unfortunately it it not because you dusted off the top of the engine. There is a high probability the MAF is either dirty or going out. My check engine light came on 4 times, but went off once by itself, but came back on shortly thereafter. The only way to get it go off was to remove the sensor and clean it (following the cleaning procedures outlined elsewhere herein). After 3 cleanings the light came back on for good. $300 later and my new MAF sensor arrived. A quick replacement and the light is now off.

Good luck.

[Buellwinkle]

Cleaning it is the way to go, just did it a few days ago on my kid's SLK230 and the light's been off since (I can reset it and a mile later it starts setting temp codes, 10 miles later it trigger a permanent code and CEL). I can tell you that besides no more check engine light, the car has new found power and shifts better. While your CEL light is not on, it may be storing temporary codes until it reaches a threshold.

If anything, the SLK320 should be easier (did an E320 and it was on top right after the airbox as it is on many cars), the SLK230 is right next to the hot radiator, ouch. You'll need a torx security bit (with a hole in the center) to remove the insert from the tube so you can clean it. I just sprayed the heck out of the gold colored pin, about 1/2" long and the entire thing, including the connector using the CRC MAF Sensor Cleaner. Put a little oil where it joins up with the intake tubing to make it easier to slide in. Hope it works out for you. If you are concerned about which it is, attach a pic of what you have.

BTW, the plastic engine covers snap off and can be difficult to pop off sometimes. Lift straight up so you don't damage any of the clips.

[Sold-on-MB's]

I just had mine replaced. The labor was only $45 so if you have any trouble with the labor, $45 is cheap. It was the cost of the MAF sensor itself that blew me away.

[contractsguy]

With shipping costs MAFs tend to sell for appx $300 + from sites on the internet.

I assume the dealer wants ~$500 plus a minimum of 1 hour for installation.

Good luck . . .

[lcdial]

So, I did it.

Everyone was right, this was a very easy project, and now I'm ready to pull the entire engine apart. Here's how it worked:

First, I pulled off the hoses that were connected to the engine cover, and then pulled off the engine cover. The engine cover is just held on by snaps and can just be pulled straight off.

With the engine cover removed, the MAF stares you right in the face at the back of the engine. It's the black circular thing with with grate. This comes out pretty easily too. You just unplug it and work it off the hose.

I then took the MAF inside and unscrewed the sensor part with a T20 Security driver. I sprayed it with electrical contact cleaner, and let it sit for about an hour to dry.

Putting it back on was as simple as taking it apart, and then, after unplugging the negative terminal on the battery - NO MORE CEL! (and the car flies).

I've driven for several miles over the course of four days and it hasn't come back yet. I have some pictures of the process if you're interested.

[page62]

Excellent! I figure I'll be facing this job one day...I even bought a bit driver set that has all sorts of exotic bits, including Security Torx.

Made in China. 15 bucks. Found it at a south side Flea Market (se habla espanol)...

[Zak 32 AMG]

Hi there,

I am very new to the SLK and the forum so forgive any ignorance that may occur!!!

I hav a 2000 SLK 320.

I have owned it for a few months now and everything has been going fine until last week.

Suddenly I have found myself at the traffic lights waiting for go and my car starts chugging as if it is about to stall, bu thasnt done so yet.

When I gonto accelerate, the car chugs a bit and then takes off as if there is something blocking it.

I have not had the same performance or acceleration since.

I read on the forum about cleaning the maf and resetting the accelarator but this hasn't worked.

I haven't got any warning lights so am unclear what the problem is as the car isn't telling me there is one directly.

Please can someone advise?

I have seen a Speed booster can take lag away but am reluctant to go that route as there had never been lag or chugging before and would rather find out what has gone wrong.

Many thanks.

Z

[Ricks170.465]

My 2001 SLK320 had an acceleration lag (2-3 sec.)from a full stop at idle, an intermittant problem that would set off a CEL. the codes on my OBDII were P0173 fuel trim and P0120 Throttle Position sensor. cleaning the MAF sensor and connectors did not help. I installed a new Bosch MAF sensor assy. and M-B (EA) Accelerator pedal module. this cured the problem excellent acceleration from a full stop, test drives good with no further CEL. Bosch MAF purchased at AutohausAZ.com $180. + free shipping