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Hi guys,

I have to say a massive thankyou to the forum. I cannot find the original post that saved me but Im posting this in the hope that it is useful for others.

My T5 1.9TDi 104PS was overrevving when changing gear. There seemed to be a small time delay between me reducing accelerator pedal pressure and the engine slowing down. Only really noticable between gear changes, and seemed to happen intermittently. It felt as if the engine would continue to rev up for about a second after lifting foot of the accelerator before the revs slowed down.

What you would expect during gear change process:
Just before gear change the pressure on accelerator would be reduced as the clutch pedal pressed in (so that the revs dont go through the roof when the engine not under load), revs should drop as soon as pressure released from accelerator. New gear selected, clutch brought back up then the accelerator pedal pushed down again to continue with acceleration.

What was actually happening:
The revs did not reduce immediately when pressure was reduced on the accelerator. There was a time delay of perhaps 1+ seconds before revs reduced. This gave illusion of throttle being 'stuck'.

I took the van to a VW specialist who could not reliably reproduce the issue (it was intermittent). They did notice slight overrevving on occasion. They said that the only way a diesel can overrev (when there is no extra fuel being pumped into the cylinders) is for oil to fuel the engine. Their best guess was that the turbo might be leaking oil, and this excess of oil was causing the engine to overrev. They warned me that the turbo might fail at any point and that I would have to immediately stall the engine to stop damage being caused by uncontrollable overrevving as oil fed from the broken turbo would be consumed by the engine.

I wasn't looking forward to paying a few hundred quid for a new turbo and was desperately trawling the forum for any other suggestions. Luckily I came across a post where someone has suffered similar symptoms and had fixed the problem by changing the clutch switch. I cant find the post now so Im not sure who to thank (apologies).

Im told that on some models the clutch switch operates the turbo waste gate. This clears a backlog of pressure when the engine revs drop from high to low. A failing switch on my clutch pedal could be failing to operate the waste gate and causing the slight overrevving effect.

I knew it was a long shot, but worth checking because a clutch switch only cost £14 (much less than a turbo)! I looked under my dash to see where the switch was and tried to operate the switch, sure enough it was worn out and would not slide in and out. I removed the switch and checked it with a multimeter - it didnt work. I could tell the unit was broken because the plastic was clearly worn and the spring inside was grinding.

I replaced the clutch switch with a new one from the VW parts desk. Immediately I noticed a difference. Smooth gear changes. No overrevving. A long shot - but well worth it. I would have been mortified to replace the turbo and find out that the overevving had been caused by the clutch switch failing all along! I have been driving the van for 4 months now without any recurring symptoms. Excellent news.

So once again, thanks to the community for posting useful tips. I hope my contribution helps someone else.

Rob
 

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you know its weird you should say this....
I bought my 1.9 T5 with 20,000 on the clock and when I first drove it the same thing was happening. I just adjusted my driving style to compensate, thinking it was a peculiarity of the fly-by wire throttle.
I will have a look at the clutch switch I think, then relearn the clutch/throttle sequence if its faulty.

Interesting post Rob.
 

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Just had the same problem with my 06 1.9TDi, changed the Clutch switch thingy ma bob and no more revs during gear change...happy days.....A:
Plus the added bonus of people NOT thinking I drive like a grandma.....T:
 

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I have just had the same thing happen to me. Driven about 300 miles today without any drama whatsoever. Stopped the engine for 2 mins at a shop 5 miles from home and then this.. Really do hope to find the same..!

Will keep you posted..
 

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Good ear…init.T:

My clutch switch was causing me problems last year. It was a different symptom to yours though.

The problem with mine was I couldn’t drive in very slow traffic in 1st or second gear with out kangarooing up the road however slowing/gently I pressed down the accelerator.

Thought I’d just add the above in case some else is lurching around town like was… worth checking that switch..

Glad you got it sorted.A:
 

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Thanks - useful post. I don't have this problem on my van, but the missus does have this problem on her Golf and we've lived with it (as you do) for a while. Time to see if it is the same principle.
 

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I had it on the computer but no faults was shown, didn't know to check the switch until reading this post, but your right you can check to see if the switch is working with the van plugged in.
 

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Hi guys,

I have to say a massive thankyou to the forum. I cannot find the original post that saved me but Im posting this in the hope that it is useful for others.

My T5 1.9TDi 104PS was overrevving when changing gear. There seemed to be a small time delay between me reducing accelerator pedal pressure and the engine slowing down. Only really noticable between gear changes, and seemed to happen intermittently. It felt as if the engine would continue to rev up for about a second after lifting foot of the accelerator before the revs slowed down.

What you would expect during gear change process:
Just before gear change the pressure on accelerator would be reduced as the clutch pedal pressed in (so that the revs dont go through the roof when the engine not under load), revs should drop as soon as pressure released from accelerator. New gear selected, clutch brought back up then the accelerator pedal pushed down again to continue with acceleration.

What was actually happening:
The revs did not reduce immediately when pressure was reduced on the accelerator. There was a time delay of perhaps 1+ seconds before revs reduced. This gave illusion of throttle being 'stuck'.

I took the van to a VW specialist who could not reliably reproduce the issue (it was intermittent). They did notice slight overrevving on occasion. They said that the only way a diesel can overrev (when there is no extra fuel being pumped into the cylinders) is for oil to fuel the engine. Their best guess was that the turbo might be leaking oil, and this excess of oil was causing the engine to overrev. They warned me that the turbo might fail at any point and that I would have to immediately stall the engine to stop damage being caused by uncontrollable overrevving as oil fed from the broken turbo would be consumed by the engine.

I wasn't looking forward to paying a few hundred quid for a new turbo and was desperately trawling the forum for any other suggestions. Luckily I came across a post where someone has suffered similar symptoms and had fixed the problem by changing the clutch switch. I cant find the post now so Im not sure who to thank (apologies).

Im told that on some models the clutch switch operates the turbo waste gate. This clears a backlog of pressure when the engine revs drop from high to low. A failing switch on my clutch pedal could be failing to operate the waste gate and causing the slight overrevving effect.

I knew it was a long shot, but worth checking because a clutch switch only cost £14 (much less than a turbo)! I looked under my dash to see where the switch was and tried to operate the switch, sure enough it was worn out and would not slide in and out. I removed the switch and checked it with a multimeter - it didnt work. I could tell the unit was broken because the plastic was clearly worn and the spring inside was grinding.

I replaced the clutch switch with a new one from the VW parts desk. Immediately I noticed a difference. Smooth gear changes. No overrevving. A long shot - but well worth it. I would have been mortified to replace the turbo and find out that the overevving had been caused by the clutch switch failing all along! I have been driving the van for 4 months now without any recurring symptoms. Excellent news.

So once again, thanks to the community for posting useful tips. I hope my contribution helps someone else.

Rob
im off to sort my van excellent post !!!!
 

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Thanks a million for this post.
Had the same problem, especially when taking off in 1st, 2nd and 3rd, holding revs. Changed the switch and back to normal!

Thanks again, 20 quid and thats sorted!

now whats the next noise!!
 

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This works in the Southern Hemisphere too!

Just recently bought a 2007 2.5 130kw. Had a massive throttle over-run and really jerky gear changes in 1st and 2nd. When taking off you basically had to short shift into 2nd, then 3rd without coming on boost, or gas it, hold on, and then wait for it to run out of puff and then change gear. Made for not a particularly nice driving experience.

After reading through these forums, i found this thread. Yesterday my new clutch switch arrived, took two minutes to fit it, and it totally fixed everything! No over-run, and silky smooth gear changes. It is truly unbelievable how such a switch could make this much difference. The next trick will be seeing if it has any effect on gas mileage.

Next project will be H&R 40mm Springs (courtesy of VeeDubMachine in UK), removing and cleaning the inlet manifold and the turbo,
and then some 20's.

Thanks to everyone on this forum. While T5s are popular vans in New Zealand, its more for commercial use as opposed to personal / camper use. So we don't have the community of enthusiasts that collectively know more than the over priced dealers!A:A:A:A:A:A:
 

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This works in the Southern Hemisphere too!

Just recently bought a 2007 2.5 130kw. Had a massive throttle over-run and really jerky gear changes in 1st and 2nd. When taking off you basically had to short shift into 2nd, then 3rd without coming on boost, or gas it, hold on, and then wait for it to run out of puff and then change gear. Made for not a particularly nice driving experience.

After reading through these forums, i found this thread. Yesterday my new clutch switch arrived, took two minutes to fit it, and it totally fixed everything! No over-run, and silky smooth gear changes. It is truly unbelievable how such a switch could make this much difference. The next trick will be seeing if it has any effect on gas mileage.

Next project will be H&R 40mm Springs (courtesy of VeeDubMachine in UK), removing and cleaning the inlet manifold and the turbo,
and then some 20's.

Thanks to everyone on this forum. While T5s are popular vans in New Zealand, its more for commercial use as opposed to personal / camper use. So we don't have the community of enthusiasts that collectively know more than the over priced dealers!A:A:A:A:A:A:
Just wondered if you fitted your new switch with the clutch pedal up or pushed down?
 
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