Hi, have an 02 110TDi Elegance estate that the wife has used for the last 3 and a half years, came home from work yesterday complainiong that something isn't right with the car, its very slow, went out thinking that she'd caught the mat under the accelerator pedal, turns out she hadn't , and the car indeed is very slow, and just will not go, you can hear the turbo whistling as it boosts as per normal, but its like the hand brake is jammed on.(It isn't).

I've just had the air intake apart and cleaned the MAF, also ran the car with the hard pipe from the turbo to intercooler disconnected, there is enough boost to knock over a full 600ml tin of carb cleaner, checked the timing and cam belt, everything seems ok, it starts and stops as it should, it just won't go, I'm beginning to wonder if its a vacuum problem, and was wondering if anyone else has had either of the solenoid switching valves on the bulkhead pack up, if so which one was it etc etc.

Many thanks in advance for reading my ramblings, and any advice/ideas will be greatly welcomed.

Cheers

Mark

If you disconnect the turbo to inlet manifold piping, you get no boost pressure in, so you get no extra pressure out to get the exhaust turbine spinning properly to make boost with; you're effectively off boost the whole time, so that proves nothing except that you need the boost in to get boost out!

Since it's not resetting when turned off, we can eliminate the usual VVT issue.

The various solonoid and wastegate valves can and do play up sometimes, and this is where a VAGCom comes in; they'll throw fault codes which can be read off to point you in the right direction.

I would try running it with the MAF disconnected first and see if they helps it.

Mine has been playing up something cronic recently. This morning all was fine for a few miles, did a left on a roundabout in 3rd, and then there was no power. Cycled the ignition on a straight bit of road and we were off again. However somedays the car car just feels totally dead (like someone has blocked off the air intake), and other days (rare) it is like a rocket.

I had exactly the same symptoms on a 1.9Tdi that I owned, I took it too the garage after being overtaken whilst going uphill by a vintage truck! It was the MAF, new item fitted and car was back to normal.

The pipe I disconnected was after the turbo and before the intercooler, it was definately boosting with quite a lot of pressure, have now also disconnected the airflow meter,which made no difference, I have a code reader, which is reporting no faults, the eml is not on, and the car isn't smoking when revved, what is an N75, as this seems to be a common fault? Is there anyone about the Tadley/Basingstoke area who will lent me their air flow meter for 2 minutes, just to try it.

Thanks Again

Mark

If you disconnect any of the pipe joints between the turbocharger compressor and the intake manifold, the engine runs on uncompressed air drawn in at that joint. You will see some air movement on the pipe from the turbo to the joint because the exhaust turbine is turned over by the mere fact of the engine running. What you will not see. irrespective of engine speed, is boost pressure at the inlet manifold, and hence inside the engine, so disconnecting those pipes doesn't actually prove anything.

As suggested elsewhere, you could try disconnecting the MAF, although that usually gives rough running rather than just down on power.

A faulty n75 affects the ability moving of the vanes in to turbo to keep the boost on at lower rpms - in a nutshell. Maximum vacuum should be at lowest rpm.

My car most of the time does not log any faults, but is a right dog some days :-(

Where is the N75 valve located?, is it one of the 2 solenoid valve things on the bulkhead behind the engine, I'm hazarding a guess its the grey topped one, I've had to change something similar on a Laguna dci that I had a couple of years ago.I've now checked all the vacuum hoses, and they're all fine, they all hold a good suck or blow, and If I suck on the one connected to the vnt actuator the linkage moves, also with the engine at idle, disconnecting the hose from the unit on the bulkhead, and you can see the vnt linkage on the turbo move a little, is it possible that this is not working at full capacity?

Thanks Again

Mark

Edited 3 April, 200917 yr by Big Mark

N75 is the right hand of that pair.

I can see my linkage movem, but I am not sure if it moves enough. WHat I am confused about is that there is movement and the pipes seem to hold vacuum, so that points to an electrical / sensor issue.... seems logical?

Fixed, just got in from work, and stuck a new MAF in it, all fine again, Yippee, means the wife can stop "yawing on my wig-wam".

Many thanks for the ideas, and mbames, good luck with yours.

Cheers

Mark

Many thanks for the ideas, and mbames, good luck with yours.

Cool, glad you got yours sorted. A new MAF fixed mine once, for a few weeks and then it started playing up again! Hopefully this won't be the case with yours.

I think mine needs more than luck..... it needs the evil spirits that hide under the bonnet exorcising! :P

Dealer exchange MAF, or where did u get yours from?

Oh... apparently Exchange units are a thing of the past. My local VW leader is saying £68.50 inc for the part, but has no stock currently.

I wonder. Mark, do you hear a relay clicking over as it goes on and off boost when cold?

Ken, I hadn't noticed one, what could that be?, the one funny noise that it has been making .... after the car starts, and starts to idle, there is a whirring noise for a couple of seconds, almost like a motorised flap is closing, but very noisily, its been doing it a few weeks now, but nothing seems amiss, and trying to track it is hard as it sounds like its coming from both sides of the engine bay.

I have no idea; it's just that I have no issues with mine, and no relay click, where Matt has a click, and lots of issues.

Ken, I hadn't noticed one, what could that be?, the one funny noise that it has been making .... after the car starts, and starts to idle, there is a whirring noise for a couple of seconds, almost like a motorised flap is closing, but very noisily, its been doing it a few weeks now, but nothing seems amiss, and trying to track it is hard as it sounds like its coming from both sides of the engine bay.

That is likely to be the air con re-circ flap I think..... - up under the glovebox I believe.

Theair con re circ flap was disconnected when the car was 2 years old, because it packed up and was clicking, dealers wouldn't touch it as it had done 130k miles, so was well out of warranty, it sounds like its coming fro, the starter motor area, could be that its returning to its start position after it has spun up to start the car, I'm not 100% sure, if it is, I'll be annoyed as itwas only changed 10k miles ago.