1999 E300TD Mass Air Issue - PeachParts Mercedes-Benz Forum

vicd · #1 08-09-2007, 03:45 PM

Hi guys,

New to this forum. I have a 1999 E300TD with 170k on it. The check engine light came on and I noticed a loss of power. Scanned it and came up with po100 (mass air). I change the mass air and reset the light, it was fine for a couple of weeks till the light came on again with the same code. I was able to defect the sensor, reset the light and it was good for a couple of more months.
As of now I'm on my fourth mass air sensor. Whenever the light would come I would reset it before I went ahead and changed the mass air sensor and it would come on instantly.
I've only been able to keep the light off for a lengthy amount of time when I install a new mass air sensor.
I'm wondering if there could be something causing the mass air sensor to short out (computer, relay...)

Any ideas would be great.

Thanks
Vic

Parrot of Doom · #2 08-09-2007, 06:29 PM

Are you running a standard MB air filter?

Try this guide:

http://forums.mercedesclub.org.uk/showthread.php?t=18298

nhdoc · #3 08-09-2007, 10:56 PM

Yeah, that would be my guess, you either have a bad filter or a leak in the intake after it that is allowing dirt to destroy them. There is a cleaner made for them too...have you tried that? Check your intake plumbing for leaks...if there is dirt or oil getting in that will surely shorten their lives.

raMBow · #4 08-09-2007, 11:47 PM

Also, remember seeing this some time back as an alternative to the factory MAF. Do not know if it has been tested here on this forum and that certainly would not be the answer to all of your repeat issues.

Hope this helps.

http://http://www.peachparts.com/shopforum/showthread.php?t=105816

vicd · #5 08-10-2007, 09:45 AM

I replace the filter everytime I've changed the sensor with a Fram replacement.
I did try cleaning it with CRC Mass Air cleaner. It didn't work.
The element seems to be intact whenever I take the sensor out to inspect.

TMAllison · #6 08-10-2007, 10:04 AM

Are you using a OEM MAF each time or an aftermarket insert?

vicd · #7 08-10-2007, 10:09 AM

I bought 2 complete from Mercedes and 1 complete from autohauz.
The

KarTek · #8 08-10-2007, 11:46 AM

The air filter housing is kind of a bugger to get on straight. (at least mine is...) Verify that it's fitting correctly. It's probably nothing to do with your problem but good to check anyway.

vicd · #9 08-13-2007, 02:35 PM

I looks like it's straight and seated nicely into the air box.

nhdoc · #10 08-13-2007, 03:05 PM

I would next check the voltage levels to make sure yours isn't getting fried by some problem elsewhere in your system. This article might be helpful:

http://www.wellsmfgcorp.com/pdf/Counterpoint3_2.pdf

They talk about a "burn off clean cycle" controlled by a relay...sounds like if this relay is stuck your MAF could burn up.

F18 · #11 08-13-2007, 03:27 PM

vicd......when you cleaned or replaced the MAF did you clean the plug? Flush it out with the CRG Cleaning or electronic cleaner. Any corrosion caused by even the humidity on thoughs contacts can cause enough of a voltage drop to trigger an an OBDII code for a MAF Failure... also check to make sure its a snug fit and has no movement......to make sure you can zip-tie the plug to the air tube that the MAF mounts into. Just a thought!

Good luck!

vicd · #12 08-13-2007, 04:05 PM

I cleaned the connector with contact cleaner and put a little dielectric grease on it.

A relay?

I couldn't get to this link.
http://www.wellsmfgcorp.com/pdf/Counterpoint3_2.pdf

F18 · #13 08-13-2007, 05:49 PM

vicd......have you had any one of the 4 MAF sensors on your car tested?
You have bought 3....so that has been about a $600 to $900 investment in plug in parts. Two of which are OEM Mercedes so have them checked by the people that sold them to you....a dealer or independent? At this point they owe you that much before you start replacing something else. If the MAFs are ok then it is wiring or the plug or the ground off the circuit from the computer.....if the MAFs are fried it may be a relay! I have yet to see a diagram for this model vehicle that shows any relay for the MAF or if it has a secondary circuit for a high temp. cleaning cycle for this Bosch unit. Some MAF systems have a cleaning circuit some do not.... Come to think of it most I have encountered were on Gas engines and not Diesel

Are there any other symptoms?....like hard starting or studder at low rpm other than just loss of power?

vicd · #14 08-14-2007, 06:38 AM

Mercedes tested the first one I replaced and confirmed it was bad, luckily they were able to defect it. The only way I've confirmed they were bad was to reset the light when I replaced the sensor and it wouldn't come back for a couple of months.
I guess I could try and Ohm out the sensor and try to find out what it's supposed to be.
The sympton other than the light coming on is a loss in power. It feels like it stops making boost.