Disabling EGR

stumo

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Yes, and I can not find any information saying otherwise. So I am going to keep on trying to figure this out!
I'm just going to chime in here and say that I have had 2 MAF failures now on 2 different vehicles. On my vehicle ('02 ML270) the original MAF ran for several years without any issue after doing the EGR mod (Cat and Flap delete also done). Then the maf started putting the car into limp mode all of a sudden. Nothing else had changed on the car over these several years. So I put in a new maf sensor, and now the new sensor has only lasted 6 months.

2nd car this has happened on is a '01 ML270 (non facelift EGR mod but still has cats but no flaps). It had a new maf that only lasted 6 months too.

Both these mafs were genuine pierberg from the dealer.

So now the thinking is that the EGR mod circuit puts too much load on the maf sensor output driver. When you look at the circuit, when the EGR PWM gets pulled low, it basically loads up the MAF output circuit with an extra load in parallel to the ECUs high impedance input. So the output of the maf sensor goes from driving basically micro amps, to driving about 25mA through that 470ohm resistor and diode. I have no idea why my original maf lasted so long compared to the new one, but since I can only get new mafs now this looks like it is going to be a problem.

I think there might need to be some kind of isolation in the circuit to keep the maf output driver only driving a high impedance, like into a transistor or opto isolator. On the other side it can still have the pulldown resistor because the transistor/isolator will be driving that part of the circuit, not the fragile maf sensor output.

Thoughts?
 
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alexanderfoti

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I'm just going to chime in here and say that I have had 2 MAF failures now on 2 different vehicles. On my vehicle ('02 ML270) the original MAF ran for several years without any issue after doing the EGR mod (Cat and Flap delete also done). Then the maf started putting the car into limp mode all of a sudden. Nothing else had changed on the car over these several years. So I put in a new maf sensor, and now the new sensor has only lasted 6 months.

2nd car this has happened on is a '01 ML270 (non facelift EGR mod but still has cats but no flaps). It had a new maf that only lasted 6 months too.

Both these mafs were genuine pierberg from the dealer.

So now the thinking is that the EGR mod circuit puts too much load on the maf sensor output driver. When you look at the circuit, when the EGR PWM gets pulled low, it basically loads up the MAF output circuit with an extra load in parallel to the ECUs high impedance input. I have no idea why my original maf lasted so long compared to the new one, but since I can only get new mafs now this looks like it is going to be a problem.

I think there might need to be some kind of isolation in the circuit to keep the maf output driver only driving a high impedance, like into a transistor or opto isolator. On the other side it can still have the pulldown resistor because the transistor/isolator will be driving that part of the circuit, not the fragile maf sensor output.

Thoughts?

I would map the EGR out rather than trying to design a circuit to feedback the EGR signal through the MAF, but thats just my 20P
 

stumo

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I would map the EGR out rather than trying to design a circuit to feedback the EGR signal through the MAF, but thats just my 20P
Yeah I think you might be right, considering the cost of genuine maf sensors. Is there a way of removing the maf limit maps as well? Where are people getting their mapping done and what tools do I need?
 

alexanderfoti

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Yeah I think you might be right, considering the cost of genuine maf sensors. Is there a way of removing the maf limit maps as well? Where are people getting their mapping done and what tools do I need?

That all becomes very specialist, best to do your own research.
 

ajlsl600

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today .economic motoring IS research,research and research again.....
 

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What are actually voltages i should have on it? How much on MAF 5? And how much on PWM from EGR? There seems to be something wrong.. No limp mode but somehow at 40-50 mp/h on tempomat it feels like it gives gas then let it go.. And speed does change, i don't imagine that, my wife feel it also. So it doesn't stay by that speed smooth it is like down the hill and up the hill.. All the time but on low speed.
 

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I'm just going to chime in here and say that I have had 2 MAF failures now on 2 different vehicles. On my vehicle ('02 ML270) the original MAF ran for several years without any issue after doing the EGR mod (Cat and Flap delete also done). Then the maf started putting the car into limp mode all of a sudden. Nothing else had changed on the car over these several years. So I put in a new maf sensor, and now the new sensor has only lasted 6 months.

2nd car this has happened on is a '01 ML270 (non facelift EGR mod but still has cats but no flaps). It had a new maf that only lasted 6 months too.

Both these mafs were genuine pierberg from the dealer.

So now the thinking is that the EGR mod circuit puts too much load on the maf sensor output driver. When you look at the circuit, when the EGR PWM gets pulled low, it basically loads up the MAF output circuit with an extra load in parallel to the ECUs high impedance input. So the output of the maf sensor goes from driving basically micro amps, to driving about 25mA through that 470ohm resistor and diode. I have no idea why my original maf lasted so long compared to the new one, but since I can only get new mafs now this looks like it is going to be a problem.

I think there might need to be some kind of isolation in the circuit to keep the maf output driver only driving a high impedance, like into a transistor or opto isolator. On the other side it can still have the pulldown resistor because the transistor/isolator will be driving that part of the circuit, not the fragile maf sensor output.

Thoughts?

Done 100K since fitting my device to the ML270 with no MAF failures. Still on original MAF at 172000km.
On another vehicle - 2016 Fiat Ducato, had my egr mapped out as no emulator available. Around $300 from memory. Any competent mapper can do it.
Ian.
 

Kaurinho

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Hallo, it's me again. So as my "test faze" came to end I decided to put everything inside the computer box to hide it and make it on proper way. I soldered all connections and i lt works nicely. As I installed it car was warm. Now I see every morning on cold start, car give me error with check engine light. No LIMP just light. I used my OBD2 and it says P0489, what could be the Problem? Every day last 3 days mornings it comes. After reseting whole day works fine, just cold start. Anyone? Thanks
 

Andrei kitner

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Hi..
I made the circuit and connected it directly to EGR wires (2 wires ..signal and 12 v ) and the third wire directly to pin 5 of the MAF (don't need to look for wires and pins inside the ECU box !! ) it works very well .. no codes no limp mode :)

w210 2.2 cdi 2001
 

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Kaurinho

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Lucky you. Congrats on success. You have luckily older engine with vacuum thing so it is easy job. I still haven't done my work done.. Still some kind of problems and errors.. Now i figured out all my components values aren't right. 1k Ohm resistor is actually 875 Ohm or so, and i can't parallel connect it to get 643 Ohm I need...
 

mdmay

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when doing this EGR delete, do you just tap in to the existing wires with extenders from the little circuit?
 

leonrsa

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when doing this EGR delete, do you just tap in to the existing wires with extenders from the little circuit?
Correct. Then the circuit is hidden in the ECU box as it is a dry and safe environment for it. Have a look at posts 104 and 105
 

stumo

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Done 100K since fitting my device to the ML270 with no MAF failures. Still on original MAF at 172000km.
You better hope that original MAF never dies, because the replacements are rubbish apparently. Mine did 300k with the last 70k of that under EGR mod loads.

I don't want to go down the mapping route because thats even more expense on top of the MAF cost. I help maintain a small fleet of private ML270s locally, so the costs add up very quickly if they are chewing through a $250 part every 6 months like they currently are.

So rather than kill yet another $250 MAF, I'm thinking about somehow emulating the MAF signal. It isn't used for engine control, its only there to allow the ECU to detect EGR malfunction, and to provide a hard limit on fuelling if there is some kind of air flow restriction.

So has anyone tried sending a constant signal on the MAF signal wire, like 4.5V? I already know that the ECU doesn't like seeing the full 5V on that line. If I feed in 4.3V say through a 470Ohm resistor and fwd biased diode from the MAF 5V supply, then when EGR is activated it will drop my new "MAF" signal by half. The rest of the time the "MAF" will be constant near full scale at 4.3V. I think I'm going to try doing this its pretty easy to rig up and remove if it doesn't work.

If that doesn't work, presumably due to the MAF not changing with engine speed, I have a further idea...

Use pin9 on the OBD2 port (RPM tach signal 12Vp-p) and condition it into a suitable DC voltage using a diode, capacitor and resistors. That can give me say 0.5 to 4.5V of MAF signal varying with RPM, exactly like a fully working MAF sensor!
 

LostKiwi

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Use pin9 on the OBD2 port (RPM tach signal 12Vp-p) and condition it into a suitable DC voltage using a diode, capacitor and resistors. That can give me say 0.5 to 4.5V of MAF signal varying with RPM, exactly like a fully working MAF sensor
Or you could use the throttle position to alter the signal. It'll exactly follow airflow that way...
 

stumo

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Or you could use the throttle position to alter the signal. It'll exactly follow airflow that way...
That wont work for 2 reasons.
1. There is no throttle.
2. Even if there was (or I used PPS instead), 100% TPS/PPS at 1000rpm should have a different MAF than 100% TPS/PPS at 4000rpm.

So MAF would only really depend on RPM, and maybe MAP.
 

stumo

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[
So has anyone tried sending a constant signal on the MAF signal wire, like 4.5V? I already know that the ECU doesn't like seeing the full 5V on that line. If I feed in 4.3V say through a 470Ohm resistor and fwd biased diode from the MAF 5V supply, then when EGR is activated it will drop my new "MAF" signal by half. The rest of the time the "MAF" will be constant near full scale at 4.3V. I think I'm going to try doing this its pretty easy to rig up and remove if it doesn't work.
OK I have tried this now and it actually works!!!

I had to play with resistor values and diode a bit to get it to not throw EGR codes.

So I ended up using a 3k3 resistor from the 5V supply (MAF plug pin4), into a LED then into the MAF signal line (MAF plug pin5). This gives me a MAF reading of 570/hub, which drops to 240/hub when EGR is 100% open. (This mod requires the EGR mod to have been done). The ECU seems to be happy with those values so far. Sorry I dont have voltage readings because I cant find my multimeter lol.

The car pulls off idle very strongly, and stays strong all the way to the 4000rpm upshift point. I've run it wide open up from standstill to 100kph uphill on the steepest longest hill I have locally and it performed beautifully, and still no codes. Have idled her for 20mins during this and no codes. Its looking pretty good I cant think of any other tests except maybe heat cycling.

I will keep running it for a week or so then will post a proper thread if it is still working then.
 
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LostKiwi

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That wont work for 2 reasons.
1. There is no throttle.
2. Even if there was (or I used PPS instead), 100% TPS/PPS at 1000rpm should have a different MAF than 100% TPS/PPS at 4000rpm.

So MAF would only really depend on RPM, and maybe MAP.
You have an accelerator pedal and rpm is easy to get....
 

stumo

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Siver benz

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I installed the mods. I believe that i got the respective wires correctly. The car at first runs well. The problem iI noticed is that there were times the ignition woutd not turn over or start the engine. Intermittent at first. I noticed after an overnight not using the car, the engine would not turn over at all. I removed the gadget and start again the car. It turned over. I defer temporarilly the installation.
What coild be the problem or reason the car will not turn over at times? Is there a specific wire size needes for the mods.? Thank you.
 

Stefan75101

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Hello from little Bulgaria! As of today, another ML 270 has an EGR shunt. Everything went really fast and it works fine. Nowhere did I find how many watts the resistors should be. Sorry I work with google translate. Are there high temperature elements?
 
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