Ubp

BillyMG · 14th April 2018, 17:35

I seem to have lost a bit of low rev oomph on my cdti... but my mpg is the best it's been in months - presumably on account of the good weather - 47mpg. The engine seems a bit throaty and I've noticed the pump seems louder than it used to when I put the ignition on. I think the UBP is a fair bet but is there any way to diagnose it using either torque or the bmw software I have for my laptop? Can I check rail pressure is at optimal levels at various revs with either of these apps and will that actually indicate a failing ubp?

Mike Noc · 14th April 2018, 18:11

If the LP fuel pressure drops too low the car will go into limp mode, so if it isn't doing that you should have enough, and if you watch the pressure on the LP side it drops when the HP pump is making higher demands, so again if it is coping with putting your foot down it should be fine lower down in the rev range.

Try unplugging the MAF and seeing if that improves things.

An easy way to check the UBP is to disconnect the outlet pipe where it plugs into the fuel filter and place the end in a large jar. With key to position II you should get a strong flow of fuel into the jar with no trapped air in it for 30 seconds to a minute, depending on your ECM.

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BillyMG · 14th April 2018, 18:55

Ok I'll give that a go. I just connected to Torque and got this fault code:

P2141 – Exhaust gas recirculation (EGR) throttle control valve – circuit low

Any thoughts?

Having done a bit of reading it looks like this may be the cause. I've blanked them off in the past with other cars by making a blanking plate from a beer tin but see this needs a kit. Has anyone had one fitted for a considerable amount of time without issue??

BillyMG · 14th April 2018, 20:02

Looking at this one as it has a lot of positive reviews...

https://rover.ebay.com/rover/0/0/0?m...2F141143689530

marinabrian · 14th April 2018, 20:23

Disconnect your EGR actuator electrical connection first, and the low pressure fuel readings should be for a twin pump system be circa 360kpa (3.6 Bar or 52 PSI) and a single pump system 420 Kpa (4.2 Bar or 60 PSI)

Airflow readings should be between 495-505 mg/stroke at idle and 620-680 mg/stroke at 3000 RPM.

Brian

Mike Noc · 14th April 2018, 21:17

Quote:

Originally Posted by BillyRover

Ok I'll give that a go. I just connected to Torque and got this fault code:

P2141 – Exhaust gas recirculation (EGR) throttle control valve – circuit low

Any thoughts?

Having done a bit of reading it looks like this may be the cause. I've blanked them off in the past with other cars by making a blanking plate from a beer tin but see this needs a kit. Has anyone had one fitted for a considerable amount of time without issue??

The EGR could well be leaking, and that could cause your fault. If things had improved with unplugging the MAF then Brian's suggestion would have identified either the EGR or MAF being at fault - he has mentioned before that unplugging the MAF disables the EGR valve operation.

You can blank the EGR if you don't want to buy a kit, but use something more substantial than a beer can. If the blank deteriorates and breaks away it could damage the engine.

super s · 14th April 2018, 21:39

couldn t he just put a screw on vacum pipe Mike? so it disable it...

Mike Noc · 14th April 2018, 21:50

He could and it would work fine as long as the EGR is gas tight and not letting by when closed.

super s · 14th April 2018, 22:03

ok... i understand now...

BillyMG · 22nd April 2018, 16:16

Just to update on this thread: I bought a blank and fitted it today after cleaning out the air intake yesterday with oven cleaner / pressure washer. Couldn't believe how much gunk came out!! Anyway she's cured - feels like a new car - I could tell as soon as I put my foot on the gas pulling off my drive it was much more responsive. Really glad I did it now. Thanks for the advice lads.

14th April 2018, 17:35	#1
BillyMG Gets stuck in MG ZT 2.5 V6 Auto Tourer (Elizabeth) / MG ZT CDTI (Farage) Join Date: Jan 2017 Location: St Helens Posts: 688 Thanks: 339 Thanked 109 Times in 89 Posts	Ubp I seem to have lost a bit of low rev oomph on my cdti... but my mpg is the best it's been in months - presumably on account of the good weather - 47mpg. The engine seems a bit throaty and I've noticed the pump seems louder than it used to when I put the ignition on. I think the UBP is a fair bet but is there any way to diagnose it using either torque or the bmw software I have for my laptop? Can I check rail pressure is at optimal levels at various revs with either of these apps and will that actually indicate a failing ubp?

14th April 2018, 18:11	#2
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: 11,553 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	If the LP fuel pressure drops too low the car will go into limp mode, so if it isn't doing that you should have enough, and if you watch the pressure on the LP side it drops when the HP pump is making higher demands, so again if it is coping with putting your foot down it should be fine lower down in the rev range. Try unplugging the MAF and seeing if that improves things. An easy way to check the UBP is to disconnect the outlet pipe where it plugs into the fuel filter and place the end in a large jar. With key to position II you should get a strong flow of fuel into the jar with no trapped air in it for 30 seconds to a minute, depending on your ECM. . Last edited by Mike Noc; 14th April 2018 at 18:15..

14th April 2018, 18:55	#3
BillyMG Gets stuck in MG ZT 2.5 V6 Auto Tourer (Elizabeth) / MG ZT CDTI (Farage) Join Date: Jan 2017 Location: St Helens Posts: 688 Thanks: 339 Thanked 109 Times in 89 Posts	Ok I'll give that a go. I just connected to Torque and got this fault code: P2141 – Exhaust gas recirculation (EGR) throttle control valve – circuit low Any thoughts? Having done a bit of reading it looks like this may be the cause. I've blanked them off in the past with other cars by making a blanking plate from a beer tin but see this needs a kit. Has anyone had one fitted for a considerable amount of time without issue?? Last edited by BillyMG; 14th April 2018 at 19:59..

14th April 2018, 20:02	#4
BillyMG Gets stuck in MG ZT 2.5 V6 Auto Tourer (Elizabeth) / MG ZT CDTI (Farage) Join Date: Jan 2017 Location: St Helens Posts: 688 Thanks: 339 Thanked 109 Times in 89 Posts	Looking at this one as it has a lot of positive reviews... https://rover.ebay.com/rover/0/0/0?m...2F141143689530

14th April 2018, 20:23	#5
marinabrian MG ZT Join Date: Jan 2011 Location: Newcastle Upon Tyne Posts: 20,151 Thanks: 3,565 Thanked 10,837 Times in 5,718 Posts	Disconnect your EGR actuator electrical connection first, and the low pressure fuel readings should be for a twin pump system be circa 360kpa (3.6 Bar or 52 PSI) and a single pump system 420 Kpa (4.2 Bar or 60 PSI) Airflow readings should be between 495-505 mg/stroke at idle and 620-680 mg/stroke at 3000 RPM. Brian

14th April 2018, 21:39	#7
super s Gets stuck in mg Join Date: Jun 2015 Location: porto Posts: 542 Thanks: 134 Thanked 40 Times in 37 Posts	couldn t he just put a screw on vacum pipe Mike? so it disable it...

14th April 2018, 21:50	#8
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: 11,553 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	He could and it would work fine as long as the EGR is gas tight and not letting by when closed.

14th April 2018, 22:03	#9
super s Gets stuck in mg Join Date: Jun 2015 Location: porto Posts: 542 Thanks: 134 Thanked 40 Times in 37 Posts	ok... i understand now...

22nd April 2018, 16:16	#10
BillyMG Gets stuck in MG ZT 2.5 V6 Auto Tourer (Elizabeth) / MG ZT CDTI (Farage) Join Date: Jan 2017 Location: St Helens Posts: 688 Thanks: 339 Thanked 109 Times in 89 Posts	Just to update on this thread: I bought a blank and fitted it today after cleaning out the air intake yesterday with oven cleaner / pressure washer. Couldn't believe how much gunk came out!! Anyway she's cured - feels like a new car - I could tell as soon as I put my foot on the gas pulling off my drive it was much more responsive. Really glad I did it now. Thanks for the advice lads.