Uneven power delivery

ninaandphil · 15th February 2023, 21:30

Hi all, I have a hard to pinpoint issue on my 75 CDTi. When driving, seemingly mostly at around 50mph, the car feels hesitant, almost like a drop in fuel pressure, but it is not consistent and almost imperceptible whilst the car drives along, the feeling gets lost as the car covers rough road surfaces. I also feel the issue more when the car is cold. The hesitancy is on / off / on for a few miles and lasts a few seconds at a time. I see no drop in RPM, the car idles fine, never stalls etc. Sometimes I think I am imagining it! Does anyone have any ideas, I have a new fuel filter on it's way, but don't think this is the issue. Maybe a duff connection on one of the fuel pumps, MAF..??? Thanks for any thoughts or if this has happened to you!

Arctic · 16th February 2023, 09:31

[QUOTE]

Quote:

Originally Posted by ninaandphil

Hi all, I have a hard to pinpoint issue on my 75 CDTi. When driving, seemingly mostly at around 50mph, the car feels hesitant, almost like a drop in fuel pressure, but it is not consistent and almost imperceptible whilst the car drives along, the feeling gets lost as the car covers rough road surfaces. I also feel the issue more when the car is cold. The hesitancy is on / off / on for a few miles and lasts a few seconds at a time. I see no drop in RPM, the car idles fine, never stalls etc. Sometimes I think I am imagining it! Does anyone have any ideas, I have a new fuel filter on it's way, but don't think this is the issue. Maybe a duff connection on one of the fuel pumps, MAF..??? Thanks for any thoughts or if this has happened to you![/QUOT

E]

Hi Phil.
Unplug the MAF for a few days to see if the symptoms go away, if so you know it could then be the MAF slowly failing.

Also when was the fuel filter last changed out?

ninaandphil · 18th February 2023, 21:52

Thanks Artic, will give the maf a try if the new fuel filter doesn't work....

bigblue75 · 19th February 2023, 15:55

I had a similar issue on a previous 75... I found the in tank pump had failed and the under bonnet pump was failing. Could be worth checking the flow from the under bonnet pump and the connections to make sure it isn't drawing air?

Good luck.

15th February 2023, 21:30	#1
ninaandphil Avid contributor MG ZT CDTi Join Date: May 2013 Location: Exford Posts: 173 Thanks: 49 Thanked 25 Times in 20 Posts	Uneven power delivery Hi all, I have a hard to pinpoint issue on my 75 CDTi. When driving, seemingly mostly at around 50mph, the car feels hesitant, almost like a drop in fuel pressure, but it is not consistent and almost imperceptible whilst the car drives along, the feeling gets lost as the car covers rough road surfaces. I also feel the issue more when the car is cold. The hesitancy is on / off / on for a few miles and lasts a few seconds at a time. I see no drop in RPM, the car idles fine, never stalls etc. Sometimes I think I am imagining it! Does anyone have any ideas, I have a new fuel filter on it's way, but don't think this is the issue. Maybe a duff connection on one of the fuel pumps, MAF..??? Thanks for any thoughts or if this has happened to you!

19th February 2023, 15:55	#4
bigblue75 older not wiser 75 Tourer Join Date: Oct 2014 Location: Falkirk Posts: 274 Thanks: 93 Thanked 46 Times in 35 Posts	If it's a two pump set up - I had a similar issue on a previous 75... I found the in tank pump had failed and the under bonnet pump was failing. Could be worth checking the flow from the under bonnet pump and the connections to make sure it isn't drawing air? Good luck.

18th February 2023, 21:52	#3
ninaandphil Avid contributor MG ZT CDTi Join Date: May 2013 Location: Exford Posts: 173 Thanks: 49 Thanked 25 Times in 20 Posts	Thanks Artic, will give the maf a try if the new fuel filter doesn't work....