Continuing boost problem - MK1 TDi

[peter.s]

I can't get to the bottom of my Mk1 TDi boost problem. I suspect the N75 valve, but I'm not sure.

I think the car over-boosts and then goes into "limp mode". I'm hesitant to call it limp mode because I've scanned for codes using GoPoint and DashCommand, but no error codes come up…

I've replaced the all the vacuum hoses and tested the N75 according to this info I found: http://www.vwt4forum.co.uk/showthread.php?t=87750
I read 15ohms on the N75 and 12.5V on the power supply - so it appears to be ok, but is there something else I should be checking? Or is there a better way to test the N75?

Any ideas are welcome...

 

[dgjdrummer]

I don't know how much investigation work you've done so far or if that's on other threads already but I would say things like:

- loose boost pipes
- sticky vanes
- split in manifold/egr connection
- turbo on way out

The last one obviously being more extreme and only if you start to notice some blue smoke in your exhaust fumes when you put your foot down. The others are straight forward enough to check/remedy fairly easily unless the sticky vanes are really badly clogged.

Sent from potato.

 

[peter.s]

Thanks for the info! There's a couple in the list I hadn't thought to check out.

I've read up on sticky vanes and how to clean them, and it looks like sticky vanes will produce the symptoms my car has - but I didn't think my car has a VGT.

I've got the 66kW model ALH motor and I thought the 66kW didn't have VGT. How can I tell by looking at he turbo?

 

[dgjdrummer]

According to Muttley (somewhat of a TDi genius round these parts) they have a variable vane turbo as standard so should be easy enough to remove the downpipe and clean the sticky vanes (or do them from the top via the EGR port if you can't get underneath).

http://www.seatcupra.net/forums/showthread.php?t=316593

Hope that helps

Sent from potato.

 

[F2 Ed]

I've done the turbo clean. It worked for a while...

 

[dgjdrummer]

As a starting point to spend £5 on a tin of Mr Muscle or foamy car equivalent it's worth trying before coughing up for a new turbo.

Quite right though, some people have great results, others see a temporary improvement and others have little to no difference afterwards!

Sent from potato.

 

[Gaz7]

The VNTs are temperamental little buggers, had big problems with a 1749vb on a friends polo, was taken out and cleaned numerous times, all times correcting the problem for about 500 miles, in the end the solution was to use the vnt ring and vanes from another turbo unit, absolutely fine since!

 

[peter.s]

According to Muttley (somewhat of a TDi genius round these parts) they have a variable vane turbo as standard so should be easy enough to remove the downpipe and clean the sticky vanes (or do them from the top via the EGR port if you can't get underneath).

http://www.seatcupra.net/forums/showthread.php?t=316593

Hope that helps

Sent from potato.

Thanks again - that is interesting reading, however I'm still a little dubious.

I've just checked the on-line store of my local auto parts dealer and they don't list a VNT turbo for the 66kw TDI. Which suggests the 66kw don't use one. But the 66kw TDI's are either AGR or ALH motors... which now brings me back to the link above.

Is ther a sure fire way of identifying which turbo I have by looking at it?

 

[Gaz7]

Your turbo should be a 1749v

And it should be vnt iirc, if there's no vnt it'd be waste gated. Post up a picture of the turbo if you can, showing the actuator. If the actuator rod runs vertically down into the middle of the chra then it's vnt.

 

[tzk]

Hello guys, here's one for you.
I`m new here i hope i`m posting well here.I have a Leon mk1 1.8t 20v cupra and i have this strange problem.
I stalled the engine once and ever since at around 3500-4000 rpm i have this hesitation, it`s not happening always but when it happens it`s sudden. After this, when i stop and drive away, it's really lumpy and the idle is really shaky. Another maybe unrelated issue, but it happens at the same time, is the dash light intensity changes, slightly, but you can notice the intensity following the engine RPM.
No errors, no codes no nothing on the dash.
Any ideas??
Best regards.

 

[Gaz7]

Should really have a new thread for this. However ! Is the problem consistent, as in, every time you drive ? I'd consider checking coil park harness, and/or coil packs. When was the last time you had a plug change ?

 

[tzk]

I just bought the car 2weeks ago and this morning is the 1st time when it happened.

 

[Gaz7]

Could also be n75.. Or DV .. Or a whole host of other things, really you need to get hold of vagcom and do a few runs, and see if anything flags up.

 

[tzk]

Ok,thanks for your help i just ordered the VAG COM console i`m waiting for it and i`ll see what it shows on it.Cheers

 

[GTJEDI]

From what I can make out you do have a vnt turbo and the symptoms defo point to sticky vanes.When my pd 150 did the same I plugged in as it happened and it came up with an overboost fault.

If you do decide to clean the vnt mechanism I would advise removing the turbo and doing it properly if you want to give it half a chance of working,I did my own and it was very simple.

AL