A buddy of mine has a 2000 E430 with about 105,000 miles. The check engine light came on, but the car ran just fine. His wife took the car to the dealership and they called to notify him the MAF was bad. Replacement parts were available and it could be fixed in a few hours, but a MAF replacement costs $500 or so.

He had it done but got the old MAF back. He says it looks visually fine, no dirt or other evidence of physical damage. Is there a way to check these out, out of the car? What typically fails? Thanks, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

The MAF has a heated film. There is never any damage you can see but eventually enough contaminents land on the film so the sensor can't give an accurate reading of air flow (starting at high airflow and slowly working down the range usually). The engine light comes on because the O2 sensor are detecting that they need to trim the fuel mixtures outside the normal range (because the mixtures are getting leaner due to MAF fault).

It's still giving a measurement, but the measurement is slowly getting inaccurate......the o2 sensors can pick this up, the ecu can't detect without another sensor giving a conflicting reading.

__________________
Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32

I'm in the midst of an air mass sensor experiment. The check engine light came on on my 94 E320 - the idle would fluctuate from normal up to about 1200 rpms, pulled a code 10 from the DM plug and a code 4 from PIN #8. Disconnecting the plug resulted in exagerated symptoms. Putting in a known to be good sensor eliminated the problem immediately. So in short - the air mass sensor clearly had failed. I tried cleaning it - with electrical contact cleaner - put it back in the car, same problems. Then took it to a jewelry store and had it ultrasonically cleaned (something discussed in another post here) - put it back in the car, car has now worked fine for a week. It operates just as it does with the good sensor in the car. So to me the conclusion is pretty clear - an air mass sensor can fail just because it gets dirty, and ultrasonic cleaning can bring it back. What I don't know at this point is how long it will now last - a few more weeks or a few more years. But ultrasonic cleaning would seem to be at least an emergency measure, to get you back on the road - and perhaps more than that. I don't really know anything about an E430 - whether it's the same technology or not. If it's similar, installation should be a few minutes, not a few hours.

Deanyal,

I had the same codes (10 on the DM/4 on the LH-SFI) on my 94 E500 although it didn't have the symptoms you described as my car idled and ran fine. I also replaced the MAF but the CEL came back (same codes) only after a few weeks. As of now, these are the only codes stored and nothing else on the other modules. I'm leaning towards replacing the wiring harness but that was just replaced at 43k miles (under MB goodwill) according to the VMI and the car currently only has 76k right now. I don't know if I should take the plunge as the harness is almost 500.- or should I check for anything else? As you know, code 4 indicate high or low voltage at MAF or short circuit? Would a bad O2 sensor cause this problem too as old sensors tend to give lean readings and the LH-SFI, trying to richen the mixture is probably operating above it's normal range thus causing high/low volatage? Any other ideas. Thanks.

WDV

Thanks guys! I will see if that works here too. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

<>

What was the cleaning agent/s ????????

I don't know - it was redish in color, and I believe water based. When I set out to do this I picked up the yellow pages and the first jewelry repair person I talked to had an interest in the subject - because he had recently used his ultrasonic jewelry cleaner to clean the injectors on his Saab, apparently very successfully. I figured I had nothing to lose, took the sensor out of the housing, removed the rubber o-ring and gave it to him. He refused payment, saying "I didn't do nothing" - meaning he just lowered it into this "bath" and took it out 30 minutes later. I'll see if I can find out what it was.

You put the entire MAF unit in there? Mine is bigger than a diamond ring...

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

This thing was about 10 by 14 inches, with a little french fry basket for dipping the parts. Maybe I can get a picture of it. The liquid, whatever it is, is bubbling a little - it looks very menacing but I don't think it is.

Good morning,

We had a field engineer tell us that the MAF sensor failures were caused
by impact damage to the sensing wire by sand or dirt. Most of these cars
had an air filter that had shrunk and caved in or wasn't sealing anymore.
When you take the sensor apart, you could see little dings and nicks on the
sensing wire with a magnifing glass. The sensor cards looked sandblasted.
MB updated the airfilters around 2000/01 with a center support rib built into
the filter to help keep their shape, but they still do it.
Over oiling K&N style filters can spell instant death for MAF sensors. The oil gets pulled out of the filter right onto the air mass.
Sometimes cleaning them with electronic parts cleaner can bring them back.

I would recommend inspecting your airfilter and housing yearly to make sure there is a complete seal on all 4 sides of the filter. Any leaking dirt should be
fairly obvious to see on the filter gasket. Check the air boxes too, some of them have been warping and not sealing due to engine heat.
Turbo diesels 98+ and AMG's can be pretty susecptable to this.

I have replaced several engines due to unfiltered leak air wearing down the cylinder walls and for some reason, these cars had several MAF's and no one ever caught on to the slow engine death being done.

Have a good day.
Dr.D

My dad always told me that the most important thing to remember when working on a car, make sure all the filters are good, he said premature engine failure can be caused by bad air filters, so Dr. Diesel is right, always make sure the filter is good and sealed properly. I would think if you have an MAF fail you need to make sure that you are properly filtered!

__________________
Brian W. Heitman

www.MBCA.org/northtexas

Join MBCA!!!

Don't overlook a dirty air filter.. it will pop a MAF related code..

It was just water and Palmolive dishwashing soap. He said he used to buy an expensive ultrasonic cleaning agent but found it didn't really work any better. He did say that he also hit it with a steam cleaner, and of course in AZ things tend to dry out very quickly.

Dr. Diesel,
Have you had any experience with the W202? There was a thread recently about the fact that the Mann air filter does not fit right. Seems to be about 1/4 inch too long which doesn't sound like much but makes a big problem fitting it in. Someone posted the problem and I had the same experience. The air box can't shrink can it?!

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I have seen several air boxes begin to shrink up. (usually the single filter box
on the exhaust manifold side of the engine style.) The ones on top of the motor seem to fair better. I have seen them squeeze in around 3-6mm on some cars. (high engine heat) The air filters have also seemingly gotten bigger. They may be trying to compensate for the fact that once the filter media in the paper filters gets damp or wet, then dries. They shrink down a little.
Some of those filters in c280's and older e320's can be a real pain to get in there correctly.
Dr.D