Momentary hesitation on boost

foggyjames · Aug 12th, 2013, 00:14

Howdy gang,

Injector saga is ongoing, but that's a story for another day...!

Has anyone had experience of a momentary hesitation, shortly after the turbo has spooled? Current behaviour goes like this....foot down, and after a moment or two the turbo spools (slightly more slowly than usual), you get a shove of torque, then it pulls back for a second or two, before pulling hard again (to redline, if you held your foot down). It appears to be related to time, as although it usually occurs at 2000rpm, it will do it a bit lower (1800 or so) in higher gears (as it takes more time to build RPM in higher gears!).

Sound at all familiar? Has anyone successfully solved this issue?

I think my TCV is probably on the way out, as the spool point has gone up from 1500 to 1700 RPM in the last few weeks, and I now have this flat spot. Clearly something going on with boost control, and that looks favourite (vacuum is healthy, and the pads aren't leaking).

cheers

James

dmsims · Aug 12th, 2013, 10:59

I had identical symptoms - turned out to be a coil pack (Vida registered a misfire on that cylinder)

Symes · Aug 12th, 2013, 11:10

Foggy has a D5, so no coil packs - but I have had a similar issue with my D5, I though it was probably the torque convertor as it seemed to occur particularly under load when 'kicking down' for an overtake on my geartronic box.

In my reply to Foggy's other post I mention that I've replaced the TCV governor and on reflection I think this symptom *might* have gone or been reduced significantly... as particularly in 'semi' mode the car has changed from being a bit of a 'Garfield' into a bit of a 'wildcat'!

reesky · Aug 12th, 2013, 13:57

Well I have a similar issue and have temporarily unplugged my engine mounts (and plugged the hose) which has helped tremendously, it's like a different car! Easy to do to eliminate these. I will be plugging them back in and living with the reduced power 'til I can afford to change 'em (next month).

TCV-wise, I saved a fortune by getting the one supplied for VAG engines and adapting it and fabricating a patch lead, as detailed elsewhere on this site. £50 instead of the £180 Volvo wanted for what is effectively an identical design. Details can be found on this site. It looks like similar mark-up is put on MAF units targeted at Volvo.

foggyjames · Aug 12th, 2013, 14:51

Thanks gang!

I'm going to look at the TCV valve tonight. For £30-odd for a VAG unit, it's almost worth replacing regardless.

Engine pads are new-ish and holding vacuum.

cheers

James

Aveton Gifford · Aug 12th, 2013, 15:36

Having been through a similar thing with my 2.0T I would say definitely change the TCV, it drove me mad for months, and the difference when it was changed was huge!

atco · Aug 23rd, 2013, 19:47

Quote:

Originally Posted by Aveton Gifford

Having been through a similar thing with my 2.0T I would say definitely change the TCV, it drove me mad for months, and the difference when it was changed was huge!

what is a tcv please

66split · Aug 23rd, 2013, 20:33

Throttle control valve. Excuse me if I'm being stupid here but diesel don't have a throttle in the true sense do they?

reesky · Aug 23rd, 2013, 20:54

Quote:

Originally Posted by 66split

Throttle control valve. Excuse me if I'm being stupid here but diesel don't have a throttle in the true sense do they?

In my case I'm talking about the turbo control (governor) valve for the D5:

http://img.photobucket.com/albums/v8...o/DSC00123.jpg

66split · Aug 23rd, 2013, 21:21

Ahhh..of course!

Aug 12th, 2013, 00:14	#1
foggyjames 300 Register Keeper Last Online: Yesterday 18:25 Join Date: Dec 2001 Location: Nottingham	Momentary hesitation on boost Howdy gang, Injector saga is ongoing, but that's a story for another day...! Has anyone had experience of a momentary hesitation, shortly after the turbo has spooled? Current behaviour goes like this....foot down, and after a moment or two the turbo spools (slightly more slowly than usual), you get a shove of torque, then it pulls back for a second or two, before pulling hard again (to redline, if you held your foot down). It appears to be related to time, as although it usually occurs at 2000rpm, it will do it a bit lower (1800 or so) in higher gears (as it takes more time to build RPM in higher gears!). Sound at all familiar? Has anyone successfully solved this issue? I think my TCV is probably on the way out, as the spool point has gone up from 1500 to 1700 RPM in the last few weeks, and I now have this flat spot. Clearly something going on with boost control, and that looks favourite (vacuum is healthy, and the pads aren't leaking). cheers James __________________ VOC 300-series Register Keeper '13 V70 D4 SE Lux '89 740 Turbo Intercooler '88 360 Turbo Intercooler '84 360 GLT '81 343 GLS R-Sport '79 343 DL '70 164

Aug 12th, 2013, 14:51	#5
foggyjames 300 Register Keeper Last Online: Yesterday 18:25 Join Date: Dec 2001 Location: Nottingham	Thanks gang! I'm going to look at the TCV valve tonight. For £30-odd for a VAG unit, it's almost worth replacing regardless. Engine pads are new-ish and holding vacuum. cheers James __________________ VOC 300-series Register Keeper '13 V70 D4 SE Lux '89 740 Turbo Intercooler '88 360 Turbo Intercooler '84 360 GLT '81 343 GLS R-Sport '79 343 DL '70 164

Aug 12th, 2013, 15:36	#6
Aveton Gifford VOC Member Last Online: Jul 9th, 2024 21:18 Join Date: Mar 2012 Location: Back on top, for now!!	Having been through a similar thing with my 2.0T I would say definitely change the TCV, it drove me mad for months, and the difference when it was changed was huge! __________________ 2004 MY S60 2.0T SE WITH A STANDARD AUTO BOX 2005 MY C70 2.0T MANUAL 2007 MY XC70 D5 AUTO

Aug 12th, 2013, 10:59	#2
dmsims Junior Member Last Online: Jun 19th, 2017 01:00 Join Date: Mar 2009 Location: Compton, Devon	I had identical symptoms - turned out to be a coil pack (Vida registered a misfire on that cylinder)

Aug 12th, 2013, 11:10	#3
Symes Master Member Last Online: Apr 10th, 2024 03:33 Join Date: Oct 2001 Location: Andover, Hants	Foggy has a D5, so no coil packs - but I have had a similar issue with my D5, I though it was probably the torque convertor as it seemed to occur particularly under load when 'kicking down' for an overtake on my geartronic box. In my reply to Foggy's other post I mention that I've replaced the TCV governor and on reflection I think this symptom might have gone or been reduced significantly... as particularly in 'semi' mode the car has changed from being a bit of a 'Garfield' into a bit of a 'wildcat'!

Aug 12th, 2013, 13:57	#4
reesky Senior Member Last Online: Jun 8th, 2022 22:38 Join Date: Oct 2008 Location: Here	Well I have a similar issue and have temporarily unplugged my engine mounts (and plugged the hose) which has helped tremendously, it's like a different car! Easy to do to eliminate these. I will be plugging them back in and living with the reduced power 'til I can afford to change 'em (next month). TCV-wise, I saved a fortune by getting the one supplied for VAG engines and adapting it and fabricating a patch lead, as detailed elsewhere on this site. £50 instead of the £180 Volvo wanted for what is effectively an identical design. Details can be found on this site. It looks like similar mark-up is put on MAF units targeted at Volvo.

Aug 23rd, 2013, 20:33	#8
66split Senior Member Last Online: May 8th, 2014 17:22 Join Date: Mar 2009 Location: Leeds	Throttle control valve. Excuse me if I'm being stupid here but diesel don't have a throttle in the true sense do they?

Aug 23rd, 2013, 21:21	#10
66split Senior Member Last Online: May 8th, 2014 17:22 Join Date: Mar 2009 Location: Leeds	Ahhh..of course!

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