MAF Sensor

[SirTweakAlot]

Pack up
I'm straight
Enough
Oh, say, say, say
Oh, say, say, say
Oh, say, say, say
Oh, say, say, say
Oh, say, say, say
Wait, they don't love you like I love you
Wait, they don't love you like I love you
MAFS
Wait, they don't love you like I love you
Made off
Don't stray
My kind's your kind
I'll stay the same
Pack up
Don't stray
Oh, say, say, say
Oh, say, say, say
Wait, they don't love you like I love you
Wait, they don't love you like I love you
MAFS
Wait, they don't love me like I love you
Wait, they don't love me like I love you
MAFS
Wait, they don't love you like I love you
Wait, they don't love you like I love you
Wait, they don't love you like I love you
MAFS, wait
They don't love me like I love you
Wait, they don't love you like I love you
MAFS
Wait, they don't love you like I love you

 

[Provet]

Wtf, lol

 

[Jon E]

On the M119 MAF, all five wires are used; four are signals to the LH module, the fifth is chassis ground. See attached photo with the schematic / wiring diagram.

LH pin 17 = Air mass signal
LH pin 23 = Air mass sensor voltage supply
LH pin 34 = Air mass sensor ground
LH pin 37 = Cleaning signal for air mass sensor

LH module pinouts: http://www.w124performance.com/docs/mb/M119/M119_LH_pinouts.pdf

Hi
My 420 is running rich and I had it diagnosed, they said it was probably a defective MAF, so I bought a used one on Ebay and it still runs rich.
Maybe I was unlucky and got another defective MAF. Or maybe its ok and the fault is somewhere else...
So after reading this, I temporary connected the old MAF (laying on the floor) with positive 12V on pin 4 and negative on pin 1.
Readings on pin 2 and 5 is 0.0 Vdc.
When connecting positive 12V on pin 3 (cleaning signal) for a second, I can see the sensor "burn" like a little light bulb,
and the reading on pin 2 and 5 is 2.1 Vdc. When blowing thru it, it shows 2.7 Vdc.

The MAF is part nr 0 280 214 004

What does this tell you guys?
How long is the cleaning signal supposed to be on?

Any help appreciated.

Jon

 

[gsxr]

The cleaning signal is supposed to heat the element for ~1 second, after every few dozen hours of engine operation (based on total airflow). Don't run the cleaning cycle again. When all else fails, RTFM (Read The Factory Manual) to learn how the MAF works. Section C at this link.

I have no idea if your testing methods are showing anything useful. The correct method is to view live data from a digital scanner. If two different MAF's made no difference, it's unlikely a third one would change anything.

Why do you think the car is running rich? Has the O2 sensor been replaced? What fault codes return after clearing? Etc.

 

[Jon E]

Thanks for a quick reply.

The car has been diagnosed two times at different workshops, one time with the old MAF and one with the "new".
Both saying its running rich, probably the MAF causing it. Last time they said the readings didnt change when they unplugged the MAF.
They replaced the O2 sensor as well, it was stuck on reading constant 850mV (if I remember correctly) new one is reading 900 +/-.
I dont know about the fault codes.
Symptoms is a little hesitation sometimes when accelerating, sometimes dont downshift when accelerating, cruise control sometimes stop working.
Also seen big black "exhaust spots" on floor after having the car idle indoors.
Other parts replaced last year is ignition plugs, upper wiring harness, distributor caps and dust shield.

I have a sensor simulator device at work. In 0-5 V mode, it can step up/down 0.1 V at a time. Is it possible to simulate the output of the MAF sensor with 0-5 V? Would the rpm at idle change when I simulate the airflow? Just to verify that the sensor input of the LH module is working?

 

[gsxr]

Something is fishy. If the shop is only looking at O2 voltage, that's not much help. They need to see the airflow reading in kg/hr. The rich condition could be due to another fault, for example a bad FPR causing excess fuel to be pulled into the manifold.

I don't think it's possible to simulate the MAF readings with voltage. The rough test is simply disconnecting the MAF and driving the car with it disconnected. This puts the injection system in a fixed operating mode (open loop). If the problem goes away completely, then you might actually have two defective MAF's. If the problem remains, you may have two good MAF's, a different root cause, and need to find a third workshop.

Any chance you have a spare LH module for testing, from either 4.2L or 5.0L engine?

 

[Jon E]

I called the diagnose guys today and asked what they did.
Unfortunately their scan tool could not read live data from the MAF, neither did they read the fuel pressure or took it for a test ride without the MAF connected.

I am going to disconnect the MAF tomorrow and take it for a ride, also check the fuel pressure myself if I can find the right fittings and a pressure gauge at work.
I dont have a LH module for testing.

Forgot to mention on last post that both of the fuel pumps are replaced with new ones.

Thanks again for good tips and info

 

[Provet]

Maybe, could be, last resort, i was having the same problem and i went through many mafs, Lh, and igniters, caps, rotors. The whole time it felt like bad maf sypmtoms. Come find out the [camshaft] timing was off the whole time, all pins lined up but the crank was far from 45. After i set it correct the power was back, not hesitattion and fast acceleration. I do remember before this and having on the sds it was giving rich signal as yours and i believe it was stuck in that mode due the cam sensor was always at fault because timing was off. Just something to consider checking if all else fails.

 

[Jon E]

I took it for a ride today with the MAF disconnected and the same symptoms appeared...
It always seems like the the hesitation appear after 15-20 mins of driving...

I did not have the right fitting to check the fuel pressure, but I am gonna get one during next week.

Will also try to check the timing.

 

[Jon E]

Hello guys
Its been a lot of late days at work lately so I havent been able to check the fuel pressure and timing.
But what I did check was diagnose with hfmscan. I dont have the full version with live data yet, but I was able to read faults.
One fault showed up: "Voltage at MAF" I dont know if it means output voltage or in to the MAF itself.
I did a quick check and measured the voltage to the MAF, it was 3.8 V. Is this correct? Or is it supposed to be 12 V?

 

[gsxr]

If there is fault code #4 on the LH module:

"Voltage at hot wire MAF sensor (B2/2) insufficient or too high, or open circuit in ground wire at hot wire MAF sensor"

... and, you had cleared this code after re-connecting the MAF, that likely indicates a bad MAF. However, this code will be stored if you drove the car with the MAF disconnected, and the code must be cleared.

I don't know any way to use a voltmeter to check the MAF. The correct way is viewing live data on HHT-Win/SDS with the engine running.

The factory diagnostic manuals specify breakout box sockets/pins which you won't have, and I don't know which wires correspond to the referenced numbers:

STAR TekInfo

manual.startekinfo.com

 

[Jon E]

I bought the full version of hfmscan today to check live readings.
It doesnt look like the MAF is giving out a signal at all...
I also tried to delete the #4 fault code regarding voltage at MAF, but it couldnt be deleted.

If anybody could help me confirm what the supply voltage to the MAF should be I would be happy.
It looks to me that its supposed to be 11-14 V?

LH pin 17 = Air mass signal = pin 5 in MAF connector
LH pin 23 = Air mass sensor voltage supply = pin 4 in MAF connector
LH pin 34 = Air mass sensor ground = pin 2 in MAF connector
LH pin 37 = Cleaning signal for air mass sensor = pin 3 in MAF connector
Engine ground = pin 1 in MAF connector

 

[gsxr]

Bosch docs indicate supply voltage should be 14V:

http://www.w124performance.com/docs/Bosch/Bosch_LH_MAF_sensors.pdf

 

[Jon E]

Thanks for the MAF manual.
Then I gotta find out why the supply voltage is missing. I am guessing it comes from the LH module?
Would been great to try with another module now.
I am gonna call some MB workshops tomorrow and check if they might have one laying around, maybe I am lucky.
We´re getting closer...

 

[Jon E]

I just may have an opportunity to buy a LH module today. Only thing is that part nr is different. Mine is 017 545 44 32, the one that I might buy is 016 545 12 32.
Will it work?

 

[gsxr]

017 545 44 32 is for a 140 chassis with 4.2L M119 engine.

016 545 12 32 is one revision earlier, but for the same 140+M119 combination

So yes, they are functionally equivalent. Neither has WOT enrichment, btw.

 

[Jon E]

Ok, then I will buy it.
Thanks again for a very quick reply

 

[Jon E]

Update.
I got my new LH module and replaced it with the old one today.
Measured 11,9V at pin 1 and 4 in the plug to the MAF
Deleted all old codes at pin 4, 6, 7 and 8 with a blink reader and took the car for a ride.
But after the engine was warmed up, the same hesitation problems appeared.
Also misfiring at idle, it was not THAT noticeable before...
Parked the car and checked it with the blink reader again. No fault codes! ?

I still dont have been able to check fuel pressure or timing.
Can the fuel pressure or timing cause these problems AFTER the engine is warmed up?

Previous owner changed the distributor caps and rotors 3 years ago (dont know which brand)
and I changed the insulators (Bosch) last year.

Any tips?

 

[markobro2]

Have you checked and or changed your coolant temp sensor? There are two sensor circuits shared in the sensor body one for the ignition computer and one for the LH Module. What your describing is exactly one of the many symptoms I was having, it turned out that the CTS was bad.

 

[Jon E]

No I havent checked the coolant temp sensor.
I will have a look at it.
Thanks

 

[Jon E]

I just looked at my screenshots from the hfmscan diagnostics that I did last week.
It was showing "Coolant 1 = 91ºC, Coolant 2 = 92ºC"
Do I still need to look at the coolant sensor, or is this saying that its working?

 

[gsxr]

I just looked at my screenshots from the hfmscan diagnostics that I did last week.
It was showing "Coolant 1 = 91ºC, Coolant 2 = 92ºC"
Do I still need to look at the coolant sensor, or is this saying that its working?

That indicates the coolant temp sensor is likely OK. The numbers should also match the temp gauge on the cluster.

There will only be a fault code for CTS if temps 1 and 2 are too far apart (they should be nearly identical).

 

[Jon E]

It's been some time and I have got my car back from the workshop where they fixed my a/c and checked the timing.
They said the timing was ok, 15 degrees before OT.

I took the car for a 30 min ride and then checked my sparkplug wires (2k Beru), all of them was 2.4-2.6k ohm. I'll guess thats ok?
It was measured with a $1000+ calibrated Fluke multimeter.

I also measured from inside the distributor to the end of the sparkplug wires. Then the results was at the lowest 3.4-3.6k ohm.
I didnt think it was supposed to be like that...
After putting it together again, the car ran great for 15 mins or so and then started the usual misfiring and hesitation.

I'm considering to buy new distributor caps and rotors, even though they were replaced with Bosch by previous owner like 3-4 years ago.
Thinking of going Bremi now. And even change the coils to.

I took some photos inside the distributor caps, both of them got some weird scratch inside. What do you think? Time for replacement?

And by the way, what is this purple and blue vacuum line? Its not connected and open, but I didnt feel anything in it while motor runnung.

 

[gsxr]

Plug boots at 2.4-2.6k is fine. The cap adds ~1k additional so 3.4-3.6k would be normal if measuring from the distributor cap bottom terminal. New coils wouldn't hurt but don't expect any change. Can you remove the new insulators and verify there is no liquid on the back side?

The caps don't look bad. The "scratch" is a manufacturing mold marking, it doesn't mean anything, new ones look the same. Did you drill the hole in the one cap? I don't know if that's a good idea. Adding slots at the top of the cap may help ventilation if you live in a high humidity climate (search the forum for details).

I'm not a fan of Bremi as they were never OEM for any Mercedes ignition components that I'm aware of. OE/Doduco rotors only, Bosch or Beru caps. If the insulators are dry and there's no sign of oil or vapor leaking from the camshaft sprocket seal, new caps/rotors should cure the problem, but it would be nice to pinpoint the root cause.

The purple and blue vacuum line connects to the air valve for the smog/emissions pump, which appears to be deleted on your car. Plug the end, or remove the line and cap off the fitting behind the headlight.

 

[gerryvz]

On US-spec cars, if that purple and blue vacuum line is disconnected from the smog pump valve, it will cause a persistent check engine light.

 

[Jon E]

Ok, thanks for fast answers! I didnt check behind the insulators this time, I replaced them last year and they were pretty dry.
I did not drill any holes in the caps, must have been the previous owner.
Going for Doduco, Bosch or Beru then
Also plugging the vacuum line.

Thanks

 

[gsxr]

To clarify... the OE Genuine rotors are made by Doduco. But you can't buy them aftermarket anymore, would need to shell out $$$ at the dealership. The OE/Doduco have properly-sized Allen bolt heads which is nice, and have a clear lacquer coating too, which other brands do not.

OE/dealer caps are Bosch and probably the same as what you'd buy aftermarket for the same price. After having encountered a defective Bosch cap out of the box I switched to Beru caps, but forum members have reported issues with all brands of caps AFAIK. Pick your poison, but consider adding the ventilation slots.

 

[Jon E]

Ok, cant find many Doduco parts online, so I guess it will be Bosch/Beru.

I found another loose cable/plug while looking at the coils. This is between the headlamp and coils. Any idea what it is for?

 

[gerryvz]

Ok, cant find many Doduco parts online, so I guess it will be Bosch/Beru.

I found another loose cable/plug while looking at the coils. This is between the headlamp and coils. Any idea what it is for?
View attachment 136773

That is the intake air temperature sensor, and is clipped into the black plastic air scoop that fits vertically behind the headlight.

The plastic air scoop is NLA from MB, and is a 400E/500E specific item. They come up here on the forum from time to time, used, and tend to go for about $100 a pair.

I've sold a few sets I've pulled off of cars in the past. The sensor uses a spring metal clip to hold it into a recess on the back of the air scoop, with the business end of the sensor fitting through a hole in the scoop into the intake air stream.

It appears your car may be missing the scoop?

Here is a photo of the air scoops, so you can see what they look like. The intake air sensor fits on the right hand scoop in the photo.

 

[gsxr]

Ok, cant find many Doduco parts online, so I guess it will be Bosch/Beru.

As explained in post #77, you would buy the OE Genuine rotor from the dealer. It's made by Doduco.

Bosch rotors have funky bolts and no wrench fits them correctly. Some people replace the bolts.

Beru rotors are now reboxed Facet and you don't want those. Search the forum for details on all of the above, it's been covered repeatedly repeatedly.

 

[Jon E]

So I got my new parts, distributor caps, rotors, coils and FPR. All Bosch.
I replaced them this weekend and now the car is running great
Since I didnt have much time this weekend, I had to replace all things at once, so I actually dont
know where the fault was... But I am just happy I finally got it to work.

Thanks again for all the help and great info guys!

Jon

 

[markobro2]

Update, I made a conversion harness and fitted Air Flow sensor and car starts and runs across the rev range. it is however running extremely rich. It seems like I am back to needing an Airflow Meter.

Follow-up, It turns out that the car was running rich due to ignition issues, I changed the plugs caps rotors and insulators 9 months ago and the car has been running perfect. I did 3d print a new MAF tube that mimics the diameter of the M119 tube as it was wider by 2cm then the MAF sensor for the Ferrari.

 

[Duh_Vinci]

...MAF sensor for the Ferrari.

Wait, did you have to use Ferrari MAF?