Seat leon 1.9 tdi throttle problem

[AHRacing]

Im looking for some advice

My leon has poor acceleration/power, which is an intermitant fault,

The turbo is spooling up and there is no boost leaks.

Sometimes when only using half throttle the problem goes away, there is great acceleration,

Other times there is great acceleration throughout the rev range (1k-3k) then a flat spot (the revs do continue to rise slowly) between 3k and 4k then picks up again.

Im unsure if it is a sensor or more mechanical. The EGR valve is clean but im unsure if it is working correctly.

Has anybody else experianced this problem?

 

[dgjdrummer]

Sounds like possible sticky vanes? This is where the vanes don't move as required so lower down the boost is fine but at higher revs the turbo isn't providing enough boost due to the slow/sticky vanes. In the worst cases the vanes move to allow boost to generate but do not close quickly enough to keep the boost from spiking, causing the engine to cut boost temporarily and therefore create a loss in power/acceleration known as "limp mode".

The turbos on the 1.9tdi are renowned for this and the best short term remedy is a turbo clean/Mr Muscle clean. This involves taking off the downpipe and spraying turbo cleaner/Mr Muscle (cheaper) directly on to the variable vanes and then moving the actuator rod up and down to loosen any crud, followed by a spirited (high revving, a lot of acceleration) drive.

There's a few guides around, have a look on TDI-Club and give that a go first. From there, double check for boost leaks and make sure that your vacuum lines aren't split anywhere.

If it turns out to be the vanes and a turbo clean helps, keep on top of this by booting it in 3rd gear on a long uphill and keeping your foot down for as long as possible to heat up the turbo and clear out any carbon build up. Hope this helps!

 

[Israar]

I had a similar problem to you, I'm not sure about what the sticky vanes are but mine is down to my waste gate sticking.

The EGR was cleaned by me, though more thoroughly by the garage who ended up putting in a plate to block off my EGR valve. Since they have put the plate in to blank off my EGR valve, I have the boost in all my gears now, though it takes slightly longer to warm up the engine and feels less powerful with the boost at least not it is consistent.

The head mechanic there told me that eventually I'm going to have to get a new turbo unless it manages to clean itself and recommended me to get on a decent run in 3rd gear and thrash it up the motorway to see if I can get any more crap out of my system.

If your's all clear (from the EGR valve) then it's more possible that what happened with mine isn't the same as yours but others could see this and maybe find that they have a similar problem as me and could resolve there's this way?

Hope you manage to get your problem sorted out mate!

--Lee

 

[AHRacing]

Thanks for the reply

I already had the downpipe off as i took the broken de cat off to make sure that wasnt causing the problem.

At the same time i checked that the turbo was free with no float/movement. but i could check the accuator.

Has anybody has a problem with the pressure sensors/switches on the bulkhead

It is like the engine is being restricted, like something isnt opening/closing when it should.

 

[dgjdrummer]

Israar's comment has made me think of something else it could be - the pipe from the exhaust manifold to the EGR is known to split quite regularly on these and if there's even a small leak from this area it severely affects the turbo as there's not enough pressure to build boost.

The TDI turbos don't have a wastegate, they are variable vanes that are opened and closed by the actuator to allow more/less exhaust gas to flow around the turbo blades and increase/decrease boost accordingly. It's worth checking the actuator moves freely and when you let go it springs back smoothly. It may be a faulty N75 (the right most valve), maybe try changing it for a second hand one that was known to be working?

 

[Israar]

The TDI turbos don't have a wastegate, they are variable vanes that are opened and closed by the actuator to allow more/less exhaust gas to flow around the turbo blades and increase/decrease boost accordingly. It's worth checking the actuator moves freely and when you let go it springs back smoothly. It may be a faulty N75 (the right most valve), maybe try changing it for a second hand one that was known to be working?

I thought it was a wastegate, guess I was well off the mark then haha! It is as you said though my vane on the turbo opens smoothly but closing it is slow (where it's sticking (sooted up right?)) Which is what was dropping my power and also stalling the engine because of the inbalance between fuel and air.

By blanking off the pipe which is directly under my EGR valve I have the power back albeit less than what it was but at least it's consistant. If the vane manages to clean itself (told to do high revs 3rd gear on a good run to get the temps up to blow it out) would I be able to have the plate removed and have my full power back? The garage said it would be better to leave it blanked off but my doubt is now with MOT as he said my emissions would be a lot higher now.

Hopefully we can pin point this for you, you said you couldn't check accuator right? Check this out and tell me if your engine does the same as mine: http://www.youtube.com/watch?v=zXbwAejqxHw.

--Lee

 

[dgjdrummer]

You might find that blanking off that pipe has helped resolve a boost or vacuum leak that was causing the over-boosting and the limp mode. I guess by stalling the engine you mean sapping the power to that of a small blender? If so then removing the EGR blanking plate and connecting it back up may just bring back the problem.

I'd try and blow the crud out as you suggested and see if the power picks up from there. It might feel like the power is down now but if it's boosting and holding power more smoothly then you're on to a winner! And loads of people have passed MOTs with the EGR blanked/removed and had no problems.

 

[shakzTDI]

Hi it doesnt allways show on diagnostics but swap the boost pressure sensor and the egr valve sensor around. Both on the bulk head held by 2 10mm bolts. You wont know it by driving but if the boost pressure sensor is gone when u switch of the engine it will shudder as it controls the shudder valve on the egr. I had that with my1. U can allways disconect maf they cause limp mode. If it is the turbo dont bother with mr muscle treatment it doesnt allways work.

 

[webcomsystems]

I'm needing a new boost pressure valve, but the guy at the motor factor says there's different models for different 1.9tdi engine types?? Is this true? EBay sells one that looks identical for £36.

 

[shakzTDI]

Theres different types depending on what engine you have. But to be honest if you take a pik and match it up in store it should be ok. I got mine from a tps and they never had that issue it was 46 plus vat. I wuldnt trust ebay parts

 

[AHRacing]

Cheers guys i will take i look at some of your solutions when the weather gets better.

At the moment, (the car has a water leak so not interior) with the cold weather, there isnt a problem, everything is running as I should be.

Thanks