Momentary hesitation on boost - Page 5

foggyjames · Jan 1st, 2015, 21:22

Limp-home and "woodpecker" solved! It was an overboost condition caused by the filter being damaged / clogged, and hence the vacuum couldn't be relieved in a timely manner. Odd, as I'd removed and cleaned it before to no effect, but I'm not going to argue! Given that those filters are notorious for clogging, I've replaced it with a length of 5mm hose and a carb fuel filter.

The original fault of the momentary hesitation is still there, but it's so much better now that I'm going to take a breather before attempting to trace that.

cheers

James

Joe Harding · Jan 2nd, 2015, 13:03

Do please check your EGR isn't full of wet soot. All parts need cleaning out thoroughly. Best place is on a pristine white table cloth spread over a polished dining-room table...

RAN60 · Jan 2nd, 2015, 14:19

Just ordered my hand woven, custom lace table cloth to get the job done

foggyjames · Jan 2nd, 2015, 19:39

EGR mixer is cleaned regularly, and I even swapped out the complete EGR valve assembly and cooler 2-3 months ago. I know exactly what you mean about the table cloth...!

cheers

James

davebb · Jan 4th, 2015, 23:40

Hi James glad to see that you found the what was making your car make the woodpecker noise, as I told you in the summer that I was getting that as well on max boost under load,how did you find it,i know that your vida was showing very high boost,i like your idea of fitting a bit of pipe and a fuel filter,
I have seen that other makers have the valve going of to the air intake,
I have fitted a boot gauge in my car and am not seeing over booting,but I will try doing that,the turbo valve is only about 16 months old and it is making the dump valve noise some times
Thanks Dave

foggyjames · Jan 4th, 2015, 23:51

I was struggling to get a good answer regarding what the boost pressure was supposed to be, which wasn't helped by my VIDA laptop dying! I couldn't get the new turbo outlet hose to stay on at first, which cemented in my mind that it was overboosting.

I started looking for causes of overboost, with stuck VNT vanes and the solenoid filter being the only two I found. I ruled out the VNT vanes on the basis that I've had three different turbos on the car since this started - one which blew, a scrapyard one which blew within 5 weeks, and a brand new one - and they were all exactly the same.

My solenoid is pretty new, too. I'd try removing the filter, and if it solves it...otherwise look at the VNT vanes. Try a vacuum pump on the actuator to see if it moves freely. It probably will, based on the otherwise good behaviour. It could be caused by blocked or restricted pipework between the turbo and engine, too. Have you checked that (starting with the dreaded gummed EGR mixer pipe)?

There is still the slightest hint of 'the woodpecker' for a split second around 2000rpm, but I think it's still very slightly overboosting, as it is still pulling the boost back a bit - you can feel two flat-spots, which appear to be time-(after application of WOT) rather than RPM-specific. They may be fuelling related, though. I'm going to pick that up after a break...and when the weather is a bit warmer!

cheers

James

davebb · Jan 6th, 2015, 21:08

Hi james
thanks for the info let me know how you get on with this,when it warms up,
I will look at my tcv filter when it warms up and I still have to do my rear drop links,
Thanks Dave

davebb · Jan 7th, 2015, 15:54

Hi James,i hope all is well,i have a cold/chest infection,so no working on the car
anyway I have just found this on vag info on setting vnt turbos,
it is very good info,

http://uk-mkivs.net/topic/34834-vnt-...oost-problems/

All the best Dave

Jan 1st, 2015, 21:22	#41
foggyjames 300 Register Keeper Last Online: Yesterday 22:32 Join Date: Dec 2001 Location: Nottingham	Limp-home and "woodpecker" solved! It was an overboost condition caused by the filter being damaged / clogged, and hence the vacuum couldn't be relieved in a timely manner. Odd, as I'd removed and cleaned it before to no effect, but I'm not going to argue! Given that those filters are notorious for clogging, I've replaced it with a length of 5mm hose and a carb fuel filter. The original fault of the momentary hesitation is still there, but it's so much better now that I'm going to take a breather before attempting to trace that. 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

Jan 2nd, 2015, 13:03	#42
Joe Harding Premier Member Last Online: Yesterday 22:43 Join Date: Oct 2010 Location: Bristol	Do please check your EGR isn't full of wet soot. All parts need cleaning out thoroughly. Best place is on a pristine white table cloth spread over a polished dining-room table... __________________ "The more people I meet the more I like my God."

Jan 2nd, 2015, 19:39	#44
foggyjames 300 Register Keeper Last Online: Yesterday 22:32 Join Date: Dec 2001 Location: Nottingham	EGR mixer is cleaned regularly, and I even swapped out the complete EGR valve assembly and cooler 2-3 months ago. I know exactly what you mean about the table cloth...! 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

Jan 4th, 2015, 23:51	#46
foggyjames 300 Register Keeper Last Online: Yesterday 22:32 Join Date: Dec 2001 Location: Nottingham	I was struggling to get a good answer regarding what the boost pressure was supposed to be, which wasn't helped by my VIDA laptop dying! I couldn't get the new turbo outlet hose to stay on at first, which cemented in my mind that it was overboosting. I started looking for causes of overboost, with stuck VNT vanes and the solenoid filter being the only two I found. I ruled out the VNT vanes on the basis that I've had three different turbos on the car since this started - one which blew, a scrapyard one which blew within 5 weeks, and a brand new one - and they were all exactly the same. My solenoid is pretty new, too. I'd try removing the filter, and if it solves it...otherwise look at the VNT vanes. Try a vacuum pump on the actuator to see if it moves freely. It probably will, based on the otherwise good behaviour. It could be caused by blocked or restricted pipework between the turbo and engine, too. Have you checked that (starting with the dreaded gummed EGR mixer pipe)? There is still the slightest hint of 'the woodpecker' for a split second around 2000rpm, but I think it's still very slightly overboosting, as it is still pulling the boost back a bit - you can feel two flat-spots, which appear to be time-(after application of WOT) rather than RPM-specific. They may be fuelling related, though. I'm going to pick that up after a break...and when the weather is a bit warmer! 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

Jan 2nd, 2015, 14:19	#43
RAN60 Master Member Last Online: Jun 12th, 2024 15:00 Join Date: Jul 2009 Location: Wales	Just ordered my hand woven, custom lace table cloth to get the job done

Jan 4th, 2015, 23:40	#45
davebb Premier Member Last Online: Jun 15th, 2024 02:12 Join Date: Aug 2013 Location: Emsworth,hants	Hi James glad to see that you found the what was making your car make the woodpecker noise, as I told you in the summer that I was getting that as well on max boost under load,how did you find it,i know that your vida was showing very high boost,i like your idea of fitting a bit of pipe and a fuel filter, I have seen that other makers have the valve going of to the air intake, I have fitted a boot gauge in my car and am not seeing over booting,but I will try doing that,the turbo valve is only about 16 months old and it is making the dump valve noise some times Thanks Dave

Jan 6th, 2015, 21:08	#47
davebb Premier Member Last Online: Jun 15th, 2024 02:12 Join Date: Aug 2013 Location: Emsworth,hants	Hi james thanks for the info let me know how you get on with this,when it warms up, I will look at my tcv filter when it warms up and I still have to do my rear drop links, Thanks Dave

Jan 7th, 2015, 15:54	#48
davebb Premier Member Last Online: Jun 15th, 2024 02:12 Join Date: Aug 2013 Location: Emsworth,hants	Hi James,i hope all is well,i have a cold/chest infection,so no working on the car anyway I have just found this on vag info on setting vnt turbos, it is very good info, http://uk-mkivs.net/topic/34834-vnt-...oost-problems/ All the best Dave

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)