Drop in Fuel Economy

pshuttle · 14th November 2008, 09:03

Hi guys,

I would be greatful for some advice regarding my 2000 Rover 75 CDT (manual). Just recently I have seen a huge drop in fuel economy - along the lines of just 300 miles per full tank!!!!

I know during Winter one would reasonably expect a reduction due to the drop in temperature, however nearly 150 miles less from a full tank seems extreme. I normally get about 450-500.

I wouldn't mind too much but I did not have great MPG figures (one of those who can never seem to get more than about 35MPG at the best of times).

I have a PSI Powerbox digital tuning box (bought before RoverRon started shipping the Synergy etc) and a MAFAM with Pierburgh MAF. I also have the Mk2 intake mod.

I have tried to isolate the problem by removing the Powerbox - (no joy). I have unplugged the MAF sensor but this has made no difference.

I am going to change all the filters and the oil on the car this weekend as a precaution but it is not yet due.

Also, I detached the pipe from the EGR valve as shown on the forums a few months back. I have not yet had the chance to push the pipe back on. Could this be the cause of the horrendous drop in fuel consumption?

This is getting expensive - please help!

Pete

pshuttle · 14th November 2008, 14:28

Nobody has any ideas?

Pete

JohnDotCom · 14th November 2008, 14:36

Generally a MAF fault but as you say no difference when disconnected this could actually point to this.
Have you checked all pipes etc for fuel leaks?
As to loose use that amount of fuel something is definitely not right.
Any chance also to get it onto a T4 just in case some fault is registering?
No sign of it running on emergency program is there?

Also all the normal checks like Tyre Pressures etc.

windrush · 14th November 2008, 14:49

Hi Pete I also have a PSI power box brought from East Coast Racing and am very p;ease with it performance and have had no problems so far keeping fingers crossed

JohnDotCom · 14th November 2008, 14:50

There is a chance I suppose also that the Mafam has gone faulty and stopped working,
without which thew Pierburg MAF won't work at all.
I would contact Ron and seek advice on that though.

Frogwell · 14th November 2008, 15:16

Quote:

Originally Posted by pshuttle

I know during Winter one would reasonably expect a reduction due to the drop in temperature, however nearly 150 miles less from a full tank seems extreme. I normally get about 450-500.

The temperature drop should actually increase your mpg as the air is denser. I always find engines more responsive in the winter and while flying, where fuel burn tends to more important, I record on average a 12 - 25% increase in fuel efficiency.

tigerchubs · 14th November 2008, 15:23

Quote:

Originally Posted by pshuttle

Hi guys,

I would be greatful for some advice regarding my 2000 Rover 75 CDT (manual). Just recently I have seen a huge drop in fuel economy - along the lines of just 300 miles per full tank!!!!

I know during Winter one would reasonably expect a reduction due to the drop in temperature, however nearly 150 miles less from a full tank seems extreme. I normally get about 450-500.

I wouldn't mind too much but I did not have great MPG figures (one of those who can never seem to get more than about 35MPG at the best of times).

I have a PSI Powerbox digital tuning box (bought before RoverRon started shipping the Synergy etc) and a MAFAM with Pierburgh MAF. I also have the Mk2 intake mod.

I have tried to isolate the problem by removing the Powerbox - (no joy). I have unplugged the MAF sensor but this has made no difference.

I am going to change all the filters and the oil on the car this weekend as a precaution but it is not yet due.

Also, I detached the pipe from the EGR valve as shown on the forums a few months back. I have not yet had the chance to push the pipe back on. Could this be the cause of the horrendous drop in fuel consumption?

This is getting expensive - please help!

Pete

I't may seem a silly question but did you block the end of the rubber vac pipe?

billnick · 14th November 2008, 19:09

mine dropped by 4mpg when my intercooler o rings failed.

bill.

pshuttle · 17th November 2008, 08:37

Hi,

Thanks for the replies guys. I should probably mention that the vehicle has now done over 165,000 miles - I should also mention that I have run the car for a few thousand miles in the past with the MAF unplugged with no detrimental effect on the fuel economy - when I plug the MAFAM back in it looks like it is doing the job properly, as I can adjust the signal and can feel the performance difference.

I would like to try and rule out the MAF as being the issue here and look further afield for the problem. Billnick mentioned the intercooler o rings, how would I be able to fault find this?

The car is in this week at Signature Preston to have a curious ABS fault fixed (sensors have been replaced to no avail) as well as an SRS light issues (not seat connectors) and is going on a T4 so hopefully if there is a problem it will be flagged up.

Pete

pondweed · 17th November 2008, 08:52

turn the box off or disconnect it.... get back to basics first for checking everything.

And clean the EGR properly and connect it again - if inside is bunged up then disconnecting pipe isn't going to have a great improvement.

14th November 2008, 09:03	#1
pshuttle Avid contributor BMW G20 320d. Previously, Rover 75 2.0 CDT Club SE and CDT Classic Join Date: Dec 2006 Location: Preston Posts: 203 Thanks: 0 Thanked 0 Times in 0 Posts	Drop in Fuel Economy Hi guys, I would be greatful for some advice regarding my 2000 Rover 75 CDT (manual). Just recently I have seen a huge drop in fuel economy - along the lines of just 300 miles per full tank!!!! I know during Winter one would reasonably expect a reduction due to the drop in temperature, however nearly 150 miles less from a full tank seems extreme. I normally get about 450-500. I wouldn't mind too much but I did not have great MPG figures (one of those who can never seem to get more than about 35MPG at the best of times). I have a PSI Powerbox digital tuning box (bought before RoverRon started shipping the Synergy etc) and a MAFAM with Pierburgh MAF. I also have the Mk2 intake mod. I have tried to isolate the problem by removing the Powerbox - (no joy). I have unplugged the MAF sensor but this has made no difference. I am going to change all the filters and the oil on the car this weekend as a precaution but it is not yet due. Also, I detached the pipe from the EGR valve as shown on the forums a few months back. I have not yet had the chance to push the pipe back on. Could this be the cause of the horrendous drop in fuel consumption? This is getting expensive - please help! Pete __________________ pshuttle - Rover 75 2.0 CDT Club SE ----------------------------------------------------------- Last edited by pshuttle; 14th November 2008 at 09:30.. Reason: grammar

14th November 2008, 14:28	#2
pshuttle Avid contributor BMW G20 320d. Previously, Rover 75 2.0 CDT Club SE and CDT Classic Join Date: Dec 2006 Location: Preston Posts: 203 Thanks: 0 Thanked 0 Times in 0 Posts	Nobody has any ideas? Pete __________________ pshuttle - Rover 75 2.0 CDT Club SE -----------------------------------------------------------

14th November 2008, 14:49	#4
windrush This is my second home December 2004 Rover 75 2ltr CDTi Connoisseur SE HL Tourer Join Date: Nov 2006 Location: Aldershot Posts: 74,464 Thanks: 2,431 Thanked 3,015 Times in 2,347 Posts	Hi Pete I also have a PSI power box brought from East Coast Racing and am very p;ease with it performance and have had no problems so far keeping fingers crossed __________________ ][SIGPIC][/SIGPIC] My Pearl Black Beauty Best regards Lilian and Derek Club Member No. 96 / Forum User No. 111 REGISTRATION to the club as a member FREE, FULL MEMBERSHIP is £10 WE WILL REMEMBER THEM

17th November 2008, 08:37	#9
pshuttle Avid contributor BMW G20 320d. Previously, Rover 75 2.0 CDT Club SE and CDT Classic Join Date: Dec 2006 Location: Preston Posts: 203 Thanks: 0 Thanked 0 Times in 0 Posts	Hi, Thanks for the replies guys. I should probably mention that the vehicle has now done over 165,000 miles - I should also mention that I have run the car for a few thousand miles in the past with the MAF unplugged with no detrimental effect on the fuel economy - when I plug the MAFAM back in it looks like it is doing the job properly, as I can adjust the signal and can feel the performance difference. I would like to try and rule out the MAF as being the issue here and look further afield for the problem. Billnick mentioned the intercooler o rings, how would I be able to fault find this? The car is in this week at Signature Preston to have a curious ABS fault fixed (sensors have been replaced to no avail) as well as an SRS light issues (not seat connectors) and is going on a T4 so hopefully if there is a problem it will be flagged up. Pete __________________ pshuttle - Rover 75 2.0 CDT Club SE ----------------------------------------------------------- Last edited by pshuttle; 17th November 2008 at 08:37.. Reason: typo

14th November 2008, 14:36	#3
JohnDotCom * Rover 75 FaceLift Tourer CDTi 170BHP Auto ConnSE 2005 Model Starlight Silver Join Date: Nov 2006 Location: Abergele Posts: 28,735 Thanks: 0 Thanked 6 Times in 5 Posts	Generally a MAF fault but as you say no difference when disconnected this could actually point to this. Have you checked all pipes etc for fuel leaks? As to loose use that amount of fuel something is definitely not right. Any chance also to get it onto a T4 just in case some fault is registering? No sign of it running on emergency program is there? Also all the normal checks like Tyre Pressures etc.

14th November 2008, 14:50	#5
JohnDotCom * Rover 75 FaceLift Tourer CDTi 170BHP Auto ConnSE 2005 Model Starlight Silver Join Date: Nov 2006 Location: Abergele Posts: 28,735 Thanks: 0 Thanked 6 Times in 5 Posts	There is a chance I suppose also that the Mafam has gone faulty and stopped working, without which thew Pierburg MAF won't work at all. I would contact Ron and seek advice on that though.

14th November 2008, 19:09	#8
billnick Loves to post ex 75 Join Date: Jan 2007 Location: Abergele Posts: 445 Thanks: 0 Thanked 0 Times in 0 Posts	mine dropped by 4mpg when my intercooler o rings failed. bill.

17th November 2008, 08:52	#10
pondweed This is my second home Waiter, Waiter! I seem to have a Roomster in my drive... Join Date: Nov 2006 Location: Sussex Posts: 3,268 Thanks: 0 Thanked 1 Time in 1 Post	turn the box off or disconnect it.... get back to basics first for checking everything. And clean the EGR properly and connect it again - if inside is bunged up then disconnecting pipe isn't going to have a great improvement.