Disconnect it and go for a drive. It should run OK.
Then reconnect it and try again, it should be better. If it's no different then the MAF unit is almost certainly U/S
Isn't that what l said?
Disconnect the MAF unit, if there's no difference....it's faulty
Fit a new one, and it runs better!
I don't recall posting that.
However my local specialist are pretty good with warranty items, but if not l'm not paying another £90.... I'll buy one of the £30 ones that they also sell.
Hear this is what you stated about MAF unit diagnostic.
I find it hard to understand how the MAF unit is causing diesel fumes into the cab.
My thoughts are (for what they are worth)
You talk about diesel fumes into the cab but go on to describe exhaust fumes, two different things which have different areas that may be at fault.
Exhaust fumes into the cab should be pretty straightforward to diagnose. The fumes are created in the cylinders and then pass through the cylinder head, exhaust manifold, turbo, exhaust front pipe, exhaust middle box, exhaust middle pipe and on to the rear box.
From this list the easiest parts to check are the pipe and boxes from the turbo if you are sure that no leaks are present there then, exhaust manifold gasket leaking, exhaust manifold cracked, exhaust to turbo gasket, turbo body cracked, turbo waste gate leaking. If all of these are sound then I am pretty sure what you are smelling is not exhaust gasses.
Diesel is something different, neat fuel pumped from the tank to the injectors under pressure the TD5 uses the injectors as a pump to gain the very high pressure prior to injecting into the cylinder but that will not rule out the ability for the diesel to leak prior to the injectors. I understand that the most common point is the fuel pressure regulator sited toward the rear of the cylinder head on the right-hand side as you sit in the driver seat.
Again if you rule out and fuel leaks then its not diesel you can smell.
You have thoughts of the MAS sensor causing this smell, the MAF sensor
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM uses the information generated by the MAF sensor to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film.
One element is controlled at ambient temperature e.g. 25 °C (77 °F) while the other is heated to 200 °C (360 °F)above this temperature e.g. 225 °C (437 °F). As air passes through the MAF sensor the hot film will be cooled.
The current required to keep the constant 200 °C (360 °F) difference provides a precise although non-linear signal of the air drawn into the engine. The MAF sensor sends a voltage of between 0 and 5 volts to the ECM, proportional to the mass of the incoming air. This calculation allows the ECM to set the EGR ratio for varying operating conditions.
So in theory the MAF sensor controls only the EGR valve but we also know that false and out of range signals from the MAF sensor can cause the ECU to react to these signals.
If this reaction is to reduce the quantity of fuel the injectors dispense then power developed will be down, you are not looking for reduced fuel injected as this would not cause the smell you describe.
An increase of fuel dispensed by the injectors (which would be more in keeping with smelling diesel) would mean an increase in power developed by your engine.
More diesel injected means more power in a diesel engine not like a petrol engine which if over fuelled would mean and over rich mixture of fuel/air un-burnt petrol and result in a smell of petrol. Diesels can take to some extent additional fuel and use it (not to the point of an hydraulic lock).
After all that I really do believe what you are smelling is not exhaust fumes as you have checked and have had it checked and why should your vehicle be different to any other and the heater be able to suck the exhaust gasses from the rear of the vehicle into the cab.
Diesel it could be if any leaks but you have dismissed this by checking.
Sorry but I am coming back to the brakes and the smell of over-heated pads entering the heater system.
The only other thing I could think of is the axel and gearbox wading breathers but that would be a long shot.
OK one more and I am done do you have the additional heater air scoop fitted on the top of the wing if so has something crawled into like a mouse and died and you can smell the rotting mouse???