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rover_75_tourer
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Discussion Starter · #1 ·
My rover 75 cdt club is only doing 37 mpg. I have replaced the sensor with the set up from rover ron with the new sensor and maf75. Both fuel pumps seem to be working but they are so quiet you need stethscope to check they are working. I pulled the hose from the fuel filter and it was delivering quickly and no air bubbles. The car does seem a bit flat and it is hard to get to rev past 3500. I changed the fuel filter and this has actualy worsened the fuel consumption. Strangely the consumption is not much better on the motorway than around town - about 4mpg better. I am not exactly a boy racer - keep to speed limit in town and about 80 - 85 mph.

Car is an estate and has done about 80,000 miles and was built in 2002

Any ideas out there? Will a diagonistic from dealer be worth doing?
 

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rover_75_tourer
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My rover 75 cdt club is only doing 37 mpg. I have replaced the sensor with the set up from rover ron with the new sensor and maf75. Both fuel pumps seem to be working but they are so quiet you need stethscope to check they are working. I pulled the hose from the fuel filter and it was delivering quickly and no air bubbles. The car does seem a bit flat and it is hard to get to rev past 3500. I changed the fuel filter and this has actualy worsened the fuel consumption. Strangely the consumption is not much better on the motorway than around town - about 4mpg better. I am not exactly a boy racer - keep to speed limit in town and about 80 - 85 mph.

Car is an estate and has done about 80,000 miles and was built in 2002

Any ideas out there? Will a diagonistic from dealer be worth doing?
Have you tried some injector cleaner? At 80000 miles the injectors can be pretty gunged up, resulting in a poor spray pattern and wasted fuel (as well as reduced performance).
 

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My rover 75 cdt club is only doing 37 mpg. I have replaced the sensor with the set up from rover ron with the new sensor and maf75. Both fuel pumps seem to be working but they are so quiet you need stethscope to check they are working. I pulled the hose from the fuel filter and it was delivering quickly and no air bubbles. The car does seem a bit flat and it is hard to get to rev past 3500. I changed the fuel filter and this has actualy worsened the fuel consumption. Strangely the consumption is not much better on the motorway than around town - about 4mpg better. I am not exactly a boy racer - keep to speed limit in town and about 80 - 85 mph.

Car is an estate and has done about 80,000 miles and was built in 2002

Any ideas out there? Will a diagonistic from dealer be worth doing?
I doubt a diagnostic check will show up anything.

CDT's won't rev over 3500rpm willingly, they are just so detuned by BMW.
If you were to fit a Tu3 or Synergy it would then rev to the red line easily, however this won't do anything for your mpg!

Is it an auto?

The tourers are less economical than the saloons due to the weight and driving at 80 - 85mph will see the mpg drop significantly from what you'd get at 70-75. The auto's are even thirstier and 37mpg from an auto tourer is probably about right at those speeds.

Otherwise check the usual things like, tyre pressures (pump up to the high speed pressure), tracking - look for uneven wear front and back.

Try sticking to 75mph and no climate control too see how much improvement you get.

Ron
 

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I would say 37mpg is fairly normal if doing short journeys around town, but would expect a big improvement on motorway. I get 46mpg++ on long journeys. And 37-40 on short journeys. Also do you reset ur Trip computer and cosumption meter before making long journey? If it hasnt been reset for a hundreds or thousands of miles its giving you a average from all them miles, so changes in consumption are slow and small.

Neil
 

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rover_75_tourer
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Discussion Starter · #5 ·
The car is a manual. I did one lot of millers imjector cleaner but nothing dramatic happened as a result. The new MAF sensor did make it brisker and a bit less flat. I had vagauley wondered if one or some of the injectors might be gummed up/bad spray pattern - what would the symptons of that be?


The sad reason for posting the thread was that at the weekend i hired one of the mercdedes transit sized vans and thought it seemed a faster drive than the rover! Quite good fuel economy too!!!
 

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The car is a manual. I did one lot of millers imjector cleaner but nothing dramatic happened as a result. The new MAF sensor did make it brisker and a bit less flat. I had vagauley wondered if one or some of the injectors might be gummed up/bad spray pattern - what would the symptons of that be?
Was the stuff you put in one where you dump an entire bottle into the tank? I think it needs to be to do a real clean, as opposed to keeping working injectors in good shape. You may well be advised to go to your local Bosch diesel diagnostic specialists for a proper check, though.

You will get poor performance and economy if fuel is being injected into the cylinders but not fully burned, for whatever reason - basically the stuff just comes out of the exhaust unburned. There are a number of reasons why this might happen, but certainly poor spray pattern is one, with the fuel being insufficiently atomized. Others (Ron?) may correct me on this but I imagine other issues such as insufficient air for the fuel injected are more likely to be picked up by engine diagnostics (and/or automatically corrected by the engine management). I don't know whether there is anything the engine management can 'know' about poor spray pattern, though - the engine thinks there is enough fuel going in for the amount of air (as measured by the MAF sensor), so as far as it's concerned, nothing is wrong.
 

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Hmmm. When I bought my ZT-T CDTi 135 auto, it was giving me about 35-36 mpg in mixed driving and also wouldn't rev over 3500. Fitting a Synergy and doing the air intake mod has improved that to 44-45 mpg in similar driving conditions and I can now redline it.

Don't measure consumption using the display, it's about 8% low in my car and I believe this is true of most of them.
 

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My ZT used to do 45mpg+ doing 140mile round trip to work (average 65mph - best 650 miles to a tank).
I now only get 35mpg doing 40mile round trip to work (average 23mph - 500 miles to a tank).

Says it all really - I think the CDTi around town just doesn't do too well in the mpg stakes -its a big car I suppose.

Ron's box's ( TU3B & MAFAM) helped the performance although I have had to take mine off as the insurance company wasn't too keen on it.



AL
 

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poor fuel economy

My rover 75 cdt club is only doing 37 mpg. I have replaced the sensor with the set up from rover ron with the new sensor and maf75. Both fuel pumps seem to be working but they are so quiet you need stethscope to check they are working. I pulled the hose from the fuel filter and it was delivering quickly and no air bubbles. The car does seem a bit flat and it is hard to get to rev past 3500. I changed the fuel filter and this has actualy worsened the fuel consumption. Strangely the consumption is not much better on the motorway than around town - about 4mpg better. I am not exactly a boy racer - keep to speed limit in town and about 80 - 85 mph.

Car is an estate and has done about 80,000 miles and was built in 2002

Any ideas out there? Will a diagonistic from dealer be worth doing?
My wifes 2001 cdt is is only doing approx 32 mpg,which I reckon is way below where it should be.It may be a heavy car,but modern common rail diesels should do far better than this,it is also very flat with little assistance apparent from the turbo.A service, new maf and air filter as well as disconnecting the egr valve have not perked it up-mpg remains to be seen....
 

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My wifes 2001 cdt is is only doing approx 32 mpg,which I reckon is way below where it should be.It may be a heavy car,but modern common rail diesels should do far better than this,it is also very flat with little assistance apparent from the turbo.A service, new maf and air filter as well as disconnecting the egr valve have not perked it up-mpg remains to be seen....
Try a Tu3, this will liven it up and may improve the mpg because you won't need to drive it so hard.
What type of maf did you fit?

Ron
 

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mg_tf
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I had the economy problem when I first purchased my ZT-T with 37 being the average. I have at last sorted the major issue (after cleaning PCV and EGR) due to an out of spec. Bosch MAF overfuelling above 2500 RPM where the fuel economy would drop to around 37MPG at 80MPH. This was diagnosed by conneting to the diagnostics port and using Digimoto software and scantool device to graph the MAF performance.

Have now fitted a Pierburg MAF with a Synergy unit, I am now averaging 42mpg (brim to brim) driving to and from work 18 miles in total. I have been on a 200+ mile round trip this weekend on A,B roads and motorway the outcome, an average of 47MPG on the OBC which I know to be accurate (on my car anyway) this was doing 75mph with the car loaded to the gunnels.

I would ( as I am sure you have) go and check all the basics as I did such as tyre pressures, air filter, binding brakes etc. Also I used Tec 2000 diesel cleaner which you can put directly into the fuel filter to give the injectors a proper clean ;-) This cleaner is a specialist cleaner which was recommended to me by a diesel specialist some years ago and transformed my mundano diesel.


At last mine is running in tip top condition, especially when you put the Synergy unit to position 2 on the dashboard switch... and she flies...
 

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I had the economy problem when I first purchased my ZT-T with 37 being the average. I have at last sorted the major issue (after cleaning PCV and EGR) due to an out of spec. Bosch MAF overfuelling above 2500 RPM where the fuel economy would drop to around 37MPG at 80MPH. This was diagnosed by conneting to the diagnostics port and using Digimoto software and scantool device to graph the MAF performance.

Have now fitted a Pierburg MAF with a Synergy unit, I am now averaging 42mpg (brim to brim) driving to and from work 18 miles in total. I have been on a 200+ mile round trip this weekend on A,B roads and motorway the outcome, an average of 47MPG on the OBC which I know to be accurate (on my car anyway) this was doing 75mph with the car loaded to the gunnels.

I would ( as I am sure you have) go and check all the basics as I did such as tyre pressures, air filter, binding brakes etc. Also I used Tec 2000 diesel cleaner which you can put directly into the fuel filter to give the injectors a proper clean ;-) This cleaner is a specialist cleaner which was recommended to me by a diesel specialist some years ago and transformed my mundano diesel.


At last mine is running in tip top condition, especially when you put the Synergy unit to position 2 on the dashboard switch... and she flies...
I am pleased to read of your successful cure for poor mpg and with the extra performance form a Synergy on tap as well. Best of both worlds!

It confirms what I've been saying for years (or seems like years!) that the maf sensor has a lot to answer for both in terms of performance and fuel consumption.
I find it all the more ironic since it is one of the chief emissions regulating sensors! Obviously that may well be true if it was reliable.....

Ron
 

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Try a Tu3, this will liven it up and may improve the mpg because you won't need to drive it so hard.
What type of maf did you fit?

Ron

Thanks for the advice Ron.The garage we took the car to must have fitted a bosch as the invoice for this is £170+vat,however I have not confirmed this.Mpg looks to have improved,but performance is still below par.I am beginning to suspect that the turbo is not working as I cannot hear it making any sound.When the cash becomes available the TU3 will be on the shopping list.

Mark
 

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I would like to confirm it was an OE MAF Sensor - they could have fitted a cheapy one and charged you for an OE one..........

Check for Bosch markings on the sensor perhaps? Never seen a cheap one, myself.
 

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Best MPG I ever had was in September 2005 53MPG over a 200 mile mainly Motorway run with a Bog standard Engine and the stupid Maf disconnected

Current consumption is probably around 35MPG the mainl difference, the car is not suitable for short journeys and the 3 mile school run it now does really hits the MPG hard

If yo want good MPG aroung town get a Citroen Picasso Hdi, 50 MPG everywhere ;)
 

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My rover 75 cdt club is only doing 37 mpg. I have replaced the sensor with the set up from rover ron with the new sensor and maf75. Both fuel pumps seem to be working but they are so quiet you need stethscope to check they are working. I pulled the hose from the fuel filter and it was delivering quickly and no air bubbles. The car does seem a bit flat and it is hard to get to rev past 3500. I changed the fuel filter and this has actualy worsened the fuel consumption. Strangely the consumption is not much better on the motorway than around town - about 4mpg better. I am not exactly a boy racer - keep to speed limit in town and about 80 - 85 mph.

Car is an estate and has done about 80,000 miles and was built in 2002

Any ideas out there? Will a diagonistic from dealer be worth doing?
check you havent got the overly restrictive baffles (some had, mine included - 2002) in the air intake above the radiator. Easiest way - take off engine cover and the inlet gubbins temporarily, and see if there is a big difference breathying direct to the airbox and filter! (someone said you might need to disconnect the battery for a little bit so that the engine will be fresh/no memory - otherwise it will have to learn the difference over a few miles and adjust accordingly)
 

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Isn't there a How-To on cleaning your MAF around here somewhere? That would get similar results.
Cleaning the maf is not guaranteed to do anything and if it does, never lasts long.
Once the maf is on its way out, there's no going back.
Its a mafam, a new Bosch maf or a Pierburgh one + Mafam or Synergy.

From recent threads, a Pierburgh maf + Synergy or mafam sems to be giving the best mpg.

Ron
 
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