MAF sensor

[DeviAngel]

I disconnected my MAF sensor yesterday while dong a MAF test (if its faulty or not) because I replaced my injectors (coded and everything by MB), QCV and everything and I still had the jerking and rough idiling. I disconnected the battery for 40 minutes and still had the problem..

I disconnected the MAF yesterday the jerking was gone etc... But the car wouldn't accelarate as it should (understandable) but no jerking with AC on also everything was okay.

I drove with disconnected MAF for around 15 km and connected it again. IT seems everything is sorted out BUT I noticed that when the MAF (I also tried it with the MAP sensor) was disconnected I got no check engine light. Xdiag and OBD reader would show all the fault codes but NO check engine light.

I also dissconnected the MAF in while the engine is running, the engine would run the same no jerking while disconnecting it, no Check Engine light nothing...

Got me thinking if the pervious owner has done something with it. How can I make it default or enable it again? Has that anything to do with the jerking and shaking of the motor?

P.S. Check Engine light works for DPF, when the Rail Pressure Sensor is disconnected ETC....
Thank you for your time.

While Driving AP and Intake Air Pressure stay at 0.9 when ignition is off or is driven (is that okay?) :

 

[supernoodle]

Each fault can be calibrated to behave as required. So some faults won't set a MIL, some will set it in the drive cycle, some after 3 drive cycles. The error reaction will normally happen as soon as the fault is confirmed, ie visible in your reader.
When you disconnect your MAF I expect, EGR will be disabled, turbo may well be disabled too.
When you disconnect the MAP, I expect turbo will be disabled or at least put into open loop more.

So don't be fooled into thinking that because you your problem goes away when disconnecting X, the problem is with X.

0.99bar is basically atmospheric as the numbers you see are absolute. I assume the intake air pressure to be the charge air pressure, so if turbo hasn't been disabled (eg by a fault) it should increase whilst driving.

 

[DeviAngel]

Each fault can be calibrated to behave as required. So some faults won't set a MIL, some will set it in the drive cycle, some after 3 drive cycles. The error reaction will normally happen as soon as the fault is confirmed, ie visible in your reader.
When you disconnect your MAF I expect, EGR will be disabled, turbo may well be disabled too.
When you disconnect the MAP, I expect turbo will be disabled or at least put into open loop more.

So don't be fooled into thinking that because you your problem goes away when disconnecting X, the problem is with X.

0.99bar is basically atmospheric as the numbers you see are absolute. I assume the intake air pressure to be the charge air pressure, so if turbo hasn't been disabled (eg by a fault) it should increase whilst driving.

Everything is connected, the AP didn't increase while driving nor the Atmosperic Pressure they stayed on 0.9 the whole time also during kickdown on the reader while driving and the turbo si working like it should, kickdown also *(this is today while the car is acting okay ). Today I have no problem after driving with it disconnected and connecting it again ( I did that yeterday as in OP). Turbo is working all the time as it should. Before I had a lot of shaking and jerking with RPM jumping from 1500 to1800 than again to 1500 or 2000 to 2300 and then again 1800 and the car was shaking on RPM's until 2500, not near/above 3000. It didn't accelerate as it should, you have to press pedal to the metal in order to start accelerating after 5 seconds after pressing the pedal, it had also rough idle especially when you turn AC on or window heater.

Pedal sensor is working, everything is working good. The problems got away after what I did with the MAF as all of the symptoms are pointing to MAF sensor. With discconected MAP the problem pressisted, with disconnected (reconnected after 13km drive ) MAF it dissappeared. The car is driving as it should after what I did. The problem is why no MIL even thou the card reader is showing faults...

New Injectors (coded), new QCV, new Pressure Regulator on the common rail, new Sensor that is all changed...

 

[supernoodle]

If that intake air pressure isn't moving that suggests there must be more than one and you a should have some other pressure parameter available, charge air, boost pressure etc

I stated why you might not get a MIL immediately. Leave disconnected for multiple cycles and I'm sure you'll see the lamp.

 

[DeviAngel]

If that intake air pressure isn't moving that suggests there must be more than one and you a should have some other pressure parameter available, charge air, boost pressure etc

I stated why you might not get a MIL immediately. Leave disconnected for multiple cycles and I'm sure you'll see the lamp.

Okay. Thank you for your time my friend, I appreciate it

Maybe I look at the wrong parameter or made the wrong choice.

I order a new one (only the sensor) it costed around 30euros in Germany. But since the 'reset' It's driving fantastic until I get new problems I won't change it.

 

[DeviAngel]

Does anyone know what sensor is this /if its a sensor? Its soaking wet in oil ..... I replaced the MAF and the MAP and after few days good driving the problem is again there...

I inspected the car today it seems before something leaked oil there...and now this sensor is soaky in oil...