Replacement MAF's for the Diesel 75 - Page 2

Johnny2R · 21st September 2014, 11:14

Quote:

Originally Posted by HarryM1BYT

Don't bother trying to get the housing out, the bottom screw for which is very difficult to access and there is really no need.

As someone who has done that in the last few days and has scraped the skin from the knuckles of his left hand, I can second that

.

vincentfishing · 21st September 2014, 19:25

more than a year ago, looking at threads about lack of power, i disconnected the maff sensor and had a totally different car power wise, i've been getting 58 mpg long trips and 44mpg around town, i've passed 2 mot's since disconnecting(but always reconnect maff plug for test then disconnect after) , i've had no other problems with the car related to disconnecting the maff sensor, SO MY QUESTION.... am i doing any long term damage to my car, if not, why bother spending money on a new maff sensor
(my car is a rover 75 cdt classic se, 2001)

okenora · 21st September 2014, 19:42

The MAF is more involved in emissions control than anything else. Usually the ECU over fuels a little when it is unplugged causing MPG to drop and smokiness tends to increase.

Where are you getting the MPG figure from ? it's a pretty decent figure.

There does not seem to be any long term damage which will be caused by the MAF being disconnected.

vincentfishing · 21st September 2014, 20:09

thanks for quick reply, must say that since losing work on medical grounds, i do drive with a very very light foot to save money, and out of boredom i check fuel consumption almost every time i fill up.(sad aren't I) i rarely go over 2000rpm, however i did notice that returning from ireland during world cup trying to get back for england game(waste of time that was !) there was very little drop in MPG doing 85MPH On way back as doing 60 mph going, must say very pleased with my car and will be getting another when i've run it into ground !

HarryM1BYT · 21st September 2014, 20:19

Quote:

Originally Posted by vincentfishing

more than a year ago, looking at threads about lack of power, i disconnected the maff sensor and had a totally different car power wise, i've been getting 58 mpg long trips and 44mpg around town, i've passed 2 mot's since disconnecting(but always reconnect maff plug for test then disconnect after) , i've had no other problems with the car related to disconnecting the maff sensor, SO MY QUESTION.... am i doing any long term damage to my car, if not, why bother spending money on a new maff sensor
(my car is a rover 75 cdt classic se, 2001)

Pretty good mpg, but keep in mind the figures used by the ECU in the absence of a MAF thus running open loop - are deliberately set to a much higher air flow than necessary, making it richer, so the engine runs well without, but consumption really has to suffer.

Working closed loop with a properly working MAF, it should inject a perfect mix of fuel to match the airflow.

Mike Noc · 21st September 2014, 20:38

As I see it Harry the CDT always runs open loop whether the MAF is connected or not - there is no analysis of the exhaust gas so nothing to close the loop.

The 'richer running' also puzzles me. The diesels aren't air throttled so take in a full charge of air each cycle, so at idle there is far more available air than needed. The ECM will fuel the engine so that it idles at the correct speed, so the MAF reading at idle shouldn't affect the fuel consumption?

Surely it is only at higher loads where there isn't enough air for complete combustion that the MAF is required to prevent over fueling and smoking, and improve economy?

johnnyb44 · 21st September 2014, 20:49

I've noticed "the warmer the days are " the less my car does to the gallon with the maf unplugged. At the moment im regularly getting around 45 to the gallon (brim to brim) as at the height of summer it was around the 41 / 42. to the gallon. Has this got anything directly to do with the maf unplugged ?

Mike Noc · 21st September 2014, 21:08

Could well be a factor. The MAF measures the mass of air available for combustion. With it unplugged the ECM uses a default map, and as temperatures rise the mass of air falls, so less air is available, and maybe not enough to ensure good economy.

75 tinkerer · 21st September 2014, 21:11

Quote:

Originally Posted by Mike Noc

As I see it Harry the CDT always runs open loop whether the MAF is connected or not - there is no analysis of the exhaust gas so nothing to close the loop.

The 'richer running' also puzzles me. The diesels aren't air throttled so take in a full charge of air each cycle, so at idle there is far more available air than needed. The ECM will fuel the engine so that it idles at the correct speed, so the MAF reading at idle shouldn't affect the fuel consumption?

Surely it is only at higher loads where there isn't enough air for complete combustion that the MAF is required to prevent over fueling and smoking, and improve economy?

Sounds obviously correct.

marinabrian · 22nd September 2014, 08:02

Quote:

Originally Posted by johnnyb44

I've noticed "the warmer the days are " the less my car does to the gallon with the maf unplugged. At the moment im regularly getting around 45 to the gallon (brim to brim) as at the height of summer it was around the 41 / 42. to the gallon. Has this got anything directly to do with the maf unplugged ?

This is because with the MAF unplugged, the inlet air temperature is pegged at -40 degrees celcius.

The ECM makes rough calculations in regards to fueling based upon engine temperature, throttle demand, and road speed.

Brian

21st September 2014, 20:38	#16
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,558 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	As I see it Harry the CDT always runs open loop whether the MAF is connected or not - there is no analysis of the exhaust gas so nothing to close the loop. The 'richer running' also puzzles me. The diesels aren't air throttled so take in a full charge of air each cycle, so at idle there is far more available air than needed. The ECM will fuel the engine so that it idles at the correct speed, so the MAF reading at idle shouldn't affect the fuel consumption? Surely it is only at higher loads where there isn't enough air for complete combustion that the MAF is required to prevent over fueling and smoking, and improve economy? Last edited by Mike Noc; 21st September 2014 at 20:48..

21st September 2014, 20:49	#17
johnnyb44 I really should get out more....... Rover 75 Join Date: Sep 2013 Location: north wales Posts: 2,708 Thanks: 1,774 Thanked 902 Times in 507 Posts	I've noticed "the warmer the days are " the less my car does to the gallon with the maf unplugged. At the moment im regularly getting around 45 to the gallon (brim to brim) as at the height of summer it was around the 41 / 42. to the gallon. Has this got anything directly to do with the maf unplugged ? __________________ Replaced pcv filter, springs, plenum spy hole mod,Bonnet cable divider mod. Wax oiled.Air con recharged. Auto box oil changed , Jules plenum guard fitted .Smoked wind deflectors fitted.S/S Compensator.Club Grill Badge kindly donated by Andyg2011..

21st September 2014, 19:25	#12
vincentfishing Loves to post rover 75cdt diesel saloon Join Date: Mar 2013 Location: Westgate on sea Posts: 441 Thanks: 21 Thanked 83 Times in 64 Posts	more than a year ago, looking at threads about lack of power, i disconnected the maff sensor and had a totally different car power wise, i've been getting 58 mpg long trips and 44mpg around town, i've passed 2 mot's since disconnecting(but always reconnect maff plug for test then disconnect after) , i've had no other problems with the car related to disconnecting the maff sensor, SO MY QUESTION.... am i doing any long term damage to my car, if not, why bother spending money on a new maff sensor (my car is a rover 75 cdt classic se, 2001)

21st September 2014, 19:42	#13
okenora Posted a thing or two Rover 75 Conn CDT SE + intelligence pack Join Date: Jun 2013 Location: Enniskillen Posts: 1,094 Thanks: 6 Thanked 141 Times in 128 Posts	The MAF is more involved in emissions control than anything else. Usually the ECU over fuels a little when it is unplugged causing MPG to drop and smokiness tends to increase. Where are you getting the MPG figure from ? it's a pretty decent figure. There does not seem to be any long term damage which will be caused by the MAF being disconnected.

21st September 2014, 20:09	#14
vincentfishing Loves to post rover 75cdt diesel saloon Join Date: Mar 2013 Location: Westgate on sea Posts: 441 Thanks: 21 Thanked 83 Times in 64 Posts	thanks for quick reply, must say that since losing work on medical grounds, i do drive with a very very light foot to save money, and out of boredom i check fuel consumption almost every time i fill up.(sad aren't I) i rarely go over 2000rpm, however i did notice that returning from ireland during world cup trying to get back for england game(waste of time that was !) there was very little drop in MPG doing 85MPH On way back as doing 60 mph going, must say very pleased with my car and will be getting another when i've run it into ground !

21st September 2014, 21:08	#18
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,558 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	Could well be a factor. The MAF measures the mass of air available for combustion. With it unplugged the ECM uses a default map, and as temperatures rise the mass of air falls, so less air is available, and maybe not enough to ensure good economy.