MAF Sensor help.....

[Sisson]

Ive always had a feeling my 2001 2.0 HDI90 was sluggish. Well its slow anyway.

Decided to check the Maf sensor first, Unplugged it and the performance of the vehicle was the same, if not slightly better.

Now to me that means the MAf sensor is knackered, shouldnt the performance be worse without the Maf plugged in?

Thanks.

[Welly]

If I remember correctly the MAF on the 90 is only there to check that the EGR is functioning (don't ask me how/why - James told me).

Try searching but we don't really come across MAF's much on here; they just seem to work and that's that

The 90 is a bit mild anyway but responds really well to chipping

[Longintooth]

Hi
The MAF sensor measures how much air is flowing and in a diesel it would send a signal to the ECU so that it can see what's happening in combination with the RPM and MAP sensor. For example it is the only sensor that reads the Turbo to establish that the flow is matching the volume of air passing and the MAP sensors the pressure from the Turbo to the inlet manifold. These two vary dependant on whether there is power demand or when it may be doing say 70 mph in the cruise with little power on. It needs this info to decide when to open the EGR valve. This is because if the pressure difference between the inlet manifold and the EGR is high the exhaust gas will not pass to the manifold. So it waits until the pressure goes low before opening the EGR valve. The reason basically that you feel no difference is because the EGR operation actually kills the power in the cylinder by cooling the burn to reduce NOX emmissions. So although you don't know it you are contravening the emission regulations if you disconnect it - it would usually put a check light on. It won't necessarily improve your performance since it cuts out anyway when you need the power, but I'll have think about this since the ECU may not know when you need power to cut it out so you may lose some power.

No, it can't because the pressure would be to high to force in EGR on power up. To clean the MAF just spray some carb cleaner onto the wire carefully - it's sensitive.

[Sisson]

Thanks for the in depth reply.

Ive put some die-electric silicon grease on the sensor, have done on all my diesels, and heard many a good review from UK and US.

One thing i do need to do is strip the EGR valve down and inlet manifold and clean it,

Next will be a remap, also done this to all my previous cars, not just for power, but economy too.

Thanks again

[Longintooth]

HI Supa
That's interesting to know I'm only assuming it would because if it is equipped with OBD 2 as the 110 is, if so it most certainly should since that is what the Yankee mandate (OBD2) was introduced to do. However, I'm not sure which models included the mandate. But I would think it should include some form of cut out or safe mode if it did fail. This is one of those situations where one needs to do some on the car checks to establish. But the system does work the same on all of the EGR systems. It is a very tricky subject because manufacturers have tried , sometimes unsuccessfully to make it work as planned. It's this problem of getting EGR into the induction manifold when Turbo charged - there has to be a pressure difference eg exhaust higher than manifold for it to work.
Sisson - don't put anything on the sensor wire it has to be absolutely clean as a whistle.