MAF is there any way to test if it's faulty

rossocorsa · 1st May 2010, 21:05

70k CDTi auto not had it long seems to be giving disappointing mpg average 35 in mixed running, mostly A roads, never bettered 40 even on a long motorway run. I've fitted an EGR by pass, done the O rings, new air filter. Temp gauge shows centre of dial and seems to warm up quite fast, engine responds well no smoke to speak of and bumper stays very clean, revs OK to 4k plus and quite sharp off the line. Haven't done air intake mod yet or cleaned the pcv (but no signs of excess pressure) to me it all points to an out of spec MAF but as I'm (permanently) skint I'm not keen to shell out if it isn't going to help. I want to go for synergy 2/pierburg maf eventually but can't really justify the expenditure at the moment. There is no evidence that it has been changed is there any way to check it out? I do have a scanguage will the MAP figures (or any others) on there give any sort of clue?

1gp · 1st May 2010, 21:16

check your engine temp properly with the on board computer , you could have a faulty thermostat, the gauges are rubbish, normally with a out of spec maf you will have a flat spot at around 1800 rpm . sometimes if you unplug it, and try it you may get a improvement, but not always the case, and dont run it for long with maf unplugged car can go into limp mode . plenty of info on here do a search for all these problems , loads on it.

2Diesels · 1st May 2010, 21:19

You'll be lucky to get much more than that out of an auto to be brutally honest, mine showed an average of 50.4 on my recent trip down to Colchester but in reality it did 39ish, manuals are way better normally

James.uk · 1st May 2010, 22:32

My last tank worked out at 36.5 mpg. My best ever was 42 mph, but that was when I lent it to a lady friend (who is lighter footed than I am

) to go touring Devon and Cornwall last summer..

...

Matt1960 · 2nd May 2010, 07:44

rossocorsa,
I only get about 32mpg from mostly short journeys of less than 10 miles, and I have changed pcv,o rings, thermostat and MAF. All of them were wrong, but no changes have made more than about 2-3mpg.
Long journeys are always better, at nearer 40mpg.
With regard the MAF, I dont think there is a readily available device for testing this thouroughly, but the simple test is disconnecting the connector plug and see if it makes any difference. I drove mine like this for a couple of weeks, but this is more a test of poor acceleration.
IMO, the synergy will not improve mpg unless the MAF is badly out of spec and is being compensated by the mafam element of the device. In fact the extra power produced by the synergy might change the driving style to make consumption worse.

We have to remember the car is very heavy, and the auto box can lose about 15% in fuel economy, and possibly worse on very short journeys.
The box only changes to top gear at about 50mph and when warm.

Matt

rossocorsa · 2nd May 2010, 09:16

Quote:

Originally Posted by 2Diesels

You'll be lucky to get much more than that out of an auto to be brutally honest, mine showed an average of 50.4 on my recent trip down to Colchester but in reality it did 39ish, manuals are way better normally

I still think for some reason it is a bit greedy. I know that folks always tend to be overly optimistic in their claims for fuel con so take all this 50mpg with a pinch of salt, the 35mpg is not brim to brim but off the usually optimistic computer reading so the real consumption may well be worse I know that auto is a lot more greedy than manual but I had to go auto box as the relatively heavy manual clutches just wouldn't suit the wife who drives the car most of the time. I realise that synergy may not improve consumption especially as my wife is quite a fast driver but I want to fit it for the extra pull as car isn't quite quick enough. Fuel consumption is similar even when I drive it on the torque so to speak rather than foot to the floor. Anyway I'm taking my scangauge out of the TF for a while and setting it up for the ZT so I can watch what is going on see if that reveals anything

ceedy · 2nd May 2010, 09:27

Same for my Zt Auto.. problem seems to me to be that for the best economy obviously you have to be in 5th gear as much as poss , which is usually around 50mph for mine to drop in, otherwise you tend to be in 4th most of the time on rural roads ??

.

But get on the motorway and the synergy mode gets applied , and the economy suffers again

..

But consumption is still better with the synergy tho' .. IMHO.

rossocorsa · 2nd May 2010, 09:32

well if I can find another 3mpg i'll be happy that's all!! My wife does 70 miles a day so it all adds up

Matt1960 · 2nd May 2010, 10:30

rossocorsa,
One of the things left for me to try is injectors, as this can aparently make a large difference if one or two have gone out of spec. But really needs a T4 session to diagnose.

Matt

rossocorsa · 2nd May 2010, 13:46

Quote:

Originally Posted by Matt1960

rossocorsa,
One of the things left for me to try is injectors, as this can aparently make a large difference if one or two have gone out of spec. But really needs a T4 session to diagnose.

Matt

I have a good local garage with a T4 however I am under intense pressure to spend no money on non essentials by the wife and apparently anything for the ZT is in that catagory!! ....so i'll not be going down that road at the moment

1st May 2010, 21:05	#1
rossocorsa Posted a thing or two None Join Date: Feb 2010 Location: GRIMSBY Posts: 1,243 Thanks: 0 Thanked 1 Time in 1 Post	MAF is there any way to test if it's faulty 70k CDTi auto not had it long seems to be giving disappointing mpg average 35 in mixed running, mostly A roads, never bettered 40 even on a long motorway run. I've fitted an EGR by pass, done the O rings, new air filter. Temp gauge shows centre of dial and seems to warm up quite fast, engine responds well no smoke to speak of and bumper stays very clean, revs OK to 4k plus and quite sharp off the line. Haven't done air intake mod yet or cleaned the pcv (but no signs of excess pressure) to me it all points to an out of spec MAF but as I'm (permanently) skint I'm not keen to shell out if it isn't going to help. I want to go for synergy 2/pierburg maf eventually but can't really justify the expenditure at the moment. There is no evidence that it has been changed is there any way to check it out? I do have a scanguage will the MAP figures (or any others) on there give any sort of clue?

1st May 2010, 22:32	#4
James.uk Passed Away 2002 Pale Blue. Rover 75 CDTi Connoisseur auto. 170K miles Join Date: Dec 2008 Location: Near the M67. Posts: 14,509 Thanks: 199 Thanked 585 Times in 397 Posts	My last tank worked out at 36.5 mpg. My best ever was 42 mph, but that was when I lent it to a lady friend (who is lighter footed than I am ) to go touring Devon and Cornwall last summer.. ... Last edited by James.uk; 2nd May 2010 at 14:08..

2nd May 2010, 09:27	#7
ceedy This is my second home All Trophy Blue ,ZT260#50 , ZT CDTI Auto, ZR105+ and 1.8T Firefrost spoiling the Set . Join Date: Nov 2006 Location: Nr Sherborne But in Somerset.. Posts: 6,077 Thanks: 916 Thanked 1,214 Times in 768 Posts	Same for my Zt Auto.. problem seems to me to be that for the best economy obviously you have to be in 5th gear as much as poss , which is usually around 50mph for mine to drop in, otherwise you tend to be in 4th most of the time on rural roads ?? . But get on the motorway and the synergy mode gets applied , and the economy suffers again .. But consumption is still better with the synergy tho' .. IMHO. __________________ The Three Bloo's Wifey's Zr105, MY CDTI & 260 #50 and Number One sons 1.8T in Firefrost When I were a lad Zero to 142 in 10.25 secs at the Pod on my Blown Norton. 210 Kart Champ in 70's

1st May 2010, 21:16	#2
1gp I really should get out more....... mgzt, 135 cdti , manual , in solar red.also own a mgtf. Join Date: Jan 2010 Location: notts. Posts: 2,105 Thanks: 28 Thanked 40 Times in 39 Posts	check your engine temp properly with the on board computer , you could have a faulty thermostat, the gauges are rubbish, normally with a out of spec maf you will have a flat spot at around 1800 rpm . sometimes if you unplug it, and try it you may get a improvement, but not always the case, and dont run it for long with maf unplugged car can go into limp mode . plenty of info on here do a search for all these problems , loads on it.

1st May 2010, 21:19	#3
2Diesels Trader ZT 260SE, Connoisseur CDT Join Date: Mar 2009 Location: The Ancient Shire Of Bedlington Posts: 12,597 Thanks: 68 Thanked 506 Times in 305 Posts	You'll be lucky to get much more than that out of an auto to be brutally honest, mine showed an average of 50.4 on my recent trip down to Colchester but in reality it did 39ish, manuals are way better normally

2nd May 2010, 07:44	#5
Matt1960 Gets stuck in Rover 75 Connoisseur SE CDT Tourer Join Date: Sep 2009 Location: Herne Bay Posts: 654 Thanks: 1 Thanked 4 Times in 4 Posts	rossocorsa, I only get about 32mpg from mostly short journeys of less than 10 miles, and I have changed pcv,o rings, thermostat and MAF. All of them were wrong, but no changes have made more than about 2-3mpg. Long journeys are always better, at nearer 40mpg. With regard the MAF, I dont think there is a readily available device for testing this thouroughly, but the simple test is disconnecting the connector plug and see if it makes any difference. I drove mine like this for a couple of weeks, but this is more a test of poor acceleration. IMO, the synergy will not improve mpg unless the MAF is badly out of spec and is being compensated by the mafam element of the device. In fact the extra power produced by the synergy might change the driving style to make consumption worse. We have to remember the car is very heavy, and the auto box can lose about 15% in fuel economy, and possibly worse on very short journeys. The box only changes to top gear at about 50mph and when warm. Matt

2nd May 2010, 09:32	#8
rossocorsa Posted a thing or two None Join Date: Feb 2010 Location: GRIMSBY Posts: 1,243 Thanks: 0 Thanked 1 Time in 1 Post	well if I can find another 3mpg i'll be happy that's all!! My wife does 70 miles a day so it all adds up

2nd May 2010, 10:30	#9
Matt1960 Gets stuck in Rover 75 Connoisseur SE CDT Tourer Join Date: Sep 2009 Location: Herne Bay Posts: 654 Thanks: 1 Thanked 4 Times in 4 Posts	rossocorsa, One of the things left for me to try is injectors, as this can aparently make a large difference if one or two have gone out of spec. But really needs a T4 session to diagnose. Matt