A MAF sensor.....why bovver?

[bigknickers]

I've just unplugged mine to check whether the old one was funked, the car is now running better, so I think to myself 'why waste my money buying a replacement?'................tell me gang why I need the thing?

[GingerMagic]

Well..... (Sharp intake of breath...)
The MAF (Mass Air Flow) helps the ECU to determine how much air is coming through it - to compare to the turbo boosting and ensuring no boost leaks - and also the air temperature to adjust the fuelling on a cold day, and there was something else too but I forget...

When it's unplugged then the ECU reverts back to a set of factory default settings which will ensure the car runs okay, but without the correct information from the MAF then it may run rich or not boost properly....

MAF sensors get covered in oily residue over time which can be cleaned but after a while only a replacement will sort the car out.

[caprixpack]

As above, but it is worth trying to give it a good blasting with carb cleaner. I did it on mine and it brought it back to life.

[bigknickers]

I don't really care what the ecu does just that it does it................I drive around west London, the speed limit varies between 20-40mph so I don't need a racing car!!...........if I drop a few mpg so what? cos I'll never recoup the £80 I've got to shell out to get a proper one.................is that it lads???

[GingerMagic]

Pretty much....
I've unplugged it on the wife's Picasso, and no ill affects after 2 years, but her engine isn't as reliant on the MAF as yours.
By all means keep it unplugged if you are just pootling round town - no running issues other than a bit of fuel.

[bigknickers]

Ging...........looks like I'm saving me £80 then!! Jeez think about the poor old public out there buying MAF sensors like there's no tomorrow for no real reason!!!!

[PeterN]

The best buy is a secondhand original from ebay, rarely are they faulty. I have a set of resistance measurements between the pins to check them.

Peter

[PeterN]

The best buy is a secondhand original from ebay, rarely are they faulty. I have a set of resistance measurements between the pins to check them.

Peter

Why does it keep doing this?

[bigknickers]

Peter, you're obviously a much cleverer bloke than I...............but, I always think when buying secondhand bits you have only got a 1 in 4 chance;

1, it could be a cheap snide part
2, it could be a working but old part that dies 6 months down the line
3, Ya get lucky with a nice lovely part that'll last for years
4, it's busted

Some of those chances involve sending back the part n losing on the postage n waiting for a replacement................that's a right load of aggro, I'd rather breathe a sigh of relief n sadly weigh out the dosh for a new bit happy in the knowledge that the said item is gonna love me n give me no problems for years to come

[GingerMagic]

A new MAF is better if you can afford it, might get one for a touch over £60 if you keep an eye out for the deals.
It seems a lot of money for a part that some cars can do without, but it's just over a pound a week over the year, which you will probably save in fuel...

I haven't changed the one on the wife's Picasso as it sits in traffic during the school run, and only does short journeys - unless it's just me in the car and I give it a right good blast - so it's not really a priority.

[bigknickers]

I've just bought the lovely thing a TPS cos once in a while my throttle don't work at all, but I wonder how many other sensors I can throw out?............what about the MAP sensor?..............I've got meself all excited n want to have a big spring clean!!! if I had enough brains n courage I'd try n throw out all that EGR stuff, but that's waaaay too scary for lil' ol me just armed with a smile, a kitchen knife n a nice shiny sledge!!!

[GingerMagic]

Definitely bin the EGR - it chokes the engine on its own excrement, sadly no sledgehammer required, just a spanner, a plate and a double jointed spine...

[stevewalsh]

Blanked my EGR Years ago, Now up to 271000 miles and still runs clean as a whistle and the wife can get about 60mpg on a steady run, I only manage 55mpg but happy with that

[frog]

The MAF (Mass Air Flow) helps the ECU to determine how much air is coming through it - to compare to the turbo boosting and ensuring no boost leaks - and also the air temperature to adjust the fuelling on a cold day, and there was something else too but I forget...

When it's unplugged then the ECU reverts back to a set of factory default settings which will ensure the car runs okay, but without the correct information from the MAF then it may run rich or not boost properly....

If the ECU detects that the MAF is not connected, it will fall back to estimating the air flow based on (boost) pressure (a.k.a. "manifold absolute pressure", MAP), with a factory-default value for the intake air temperature (IAT). Since the IAT is measured in Kelvin, not having the exact temperature (as provided by the MAF) means that the thus calculated air mass is only a very small percentage off. See also here.

The resulting ride is pretty much the same as with MAF, but it misses the "sharp edges", and seems to be a little less fuel-efficient. As is my experience.