A MAF sensor.....why bovver?

Discuss, ask, or get help with engine and mechanical queries in here.

Moderator: Moderators

Post Reply
bigknickers
1.8 16v
Posts: 81
Joined: Mon Oct 25, 2010 6:09 pm

A MAF sensor.....why bovver?

Post by bigknickers » Sat Mar 31, 2018 5:52 pm

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?

User avatar
GingerMagic
3.0 24v
Posts: 3047
Joined: Fri Apr 06, 2012 9:02 pm
Location: Bournemouth

Re: A MAF sensor.....why bovver?

Post by GingerMagic » Sat Mar 31, 2018 6:06 pm

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.
1999 T4 family wagon
2005 Vauxhall Meriva
1998 406 V6 Coupe - Midlife crisis..!
PP2000 user, can help with faults / diagnostics in the Bournemouth area.

caprixpack
2.0 16v
Posts: 141
Joined: Sun Mar 11, 2018 5:00 pm
Location: Cumbria

Re: A MAF sensor.....why bovver?

Post by caprixpack » Sat Mar 31, 2018 6:17 pm

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.
1984 924 2.0 n/a crystal Green - The daily
2005 VW Passat tdi 130 Highline, now 170bhp & 290ft/lb
2000 Peugeot 406 2.0 hdi - stood for 4 years, fresh mot and mostly working.

bigknickers
1.8 16v
Posts: 81
Joined: Mon Oct 25, 2010 6:09 pm

Re: A MAF sensor.....why bovver?

Post by bigknickers » Sat Mar 31, 2018 6:24 pm

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???

User avatar
GingerMagic
3.0 24v
Posts: 3047
Joined: Fri Apr 06, 2012 9:02 pm
Location: Bournemouth

Re: A MAF sensor.....why bovver?

Post by GingerMagic » Sat Mar 31, 2018 6:34 pm

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.
1999 T4 family wagon
2005 Vauxhall Meriva
1998 406 V6 Coupe - Midlife crisis..!
PP2000 user, can help with faults / diagnostics in the Bournemouth area.

bigknickers
1.8 16v
Posts: 81
Joined: Mon Oct 25, 2010 6:09 pm

Re: A MAF sensor.....why bovver?

Post by bigknickers » Sat Mar 31, 2018 6:49 pm

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
3.0 24v
Posts: 1419
Joined: Sun Mar 04, 2012 7:04 pm
Location: Charmouth, Dorset

Re: A MAF sensor.....why bovver?

Post by PeterN » Sun Apr 01, 2018 10:16 am

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
3.0 24v
Posts: 1419
Joined: Sun Mar 04, 2012 7:04 pm
Location: Charmouth, Dorset

Re: A MAF sensor.....why bovver?

Post by PeterN » Sun Apr 01, 2018 10:16 am

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
1.8 16v
Posts: 81
Joined: Mon Oct 25, 2010 6:09 pm

Re: A MAF sensor.....why bovver?

Post by bigknickers » Sun Apr 01, 2018 2:49 pm

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

User avatar
GingerMagic
3.0 24v
Posts: 3047
Joined: Fri Apr 06, 2012 9:02 pm
Location: Bournemouth

Re: A MAF sensor.....why bovver?

Post by GingerMagic » Sun Apr 01, 2018 4:11 pm

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.
1999 T4 family wagon
2005 Vauxhall Meriva
1998 406 V6 Coupe - Midlife crisis..!
PP2000 user, can help with faults / diagnostics in the Bournemouth area.

bigknickers
1.8 16v
Posts: 81
Joined: Mon Oct 25, 2010 6:09 pm

Re: A MAF sensor.....why bovver?

Post by bigknickers » Sun Apr 01, 2018 4:57 pm

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!!!

User avatar
GingerMagic
3.0 24v
Posts: 3047
Joined: Fri Apr 06, 2012 9:02 pm
Location: Bournemouth

Re: A MAF sensor.....why bovver?

Post by GingerMagic » Sun Apr 01, 2018 5:05 pm

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...
1999 T4 family wagon
2005 Vauxhall Meriva
1998 406 V6 Coupe - Midlife crisis..!
PP2000 user, can help with faults / diagnostics in the Bournemouth area.

stevewalsh
2.0 16v
Posts: 108
Joined: Wed Apr 21, 2010 10:30 am
Location: SW France

Re: A MAF sensor.....why bovver?

Post by stevewalsh » Sun Apr 01, 2018 6:01 pm

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
2.0 16v
Posts: 171
Joined: Sun Aug 24, 2014 12:18 pm
Location: Netherlands

Re: A MAF sensor.....why bovver?

Post by frog » Tue Apr 03, 2018 7:00 am

GingerMagic wrote:
Sat Mar 31, 2018 6:06 pm
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.
Current "fleet":
2003 406 Estate 2.0HDi 110 - 7 seater
2001 Citroen Saxo 1.6i 8v 100

Previously owned:
2000 406 Sedan 2.0 HDi 90
2000 406 Coupé 2.0i 16v 138 - Riviera Blue

PP2000 user, can help with faults / diagnostics in the Netherlands.

Post Reply