My TDI has become a moody teenager as it approches 13 (well 130k miles!). The symptoms I'm getting are as follows -

 

• turbo is flat below 2000rpm then suddenly bursts into life, before it was smooth from about 1500 and would come on progressively
• Sometimes it feels like the car isn't pulling very well at 2500+ rpm. 
• mpg is down I think, even once warm. 
• temp sometimes drops below 90 on the gauge by 2-3 degrees even when it is 7-8oC out.

 

I've also been getting limp mode a bit worse recently, but I think it's because the car hasn't had a good run out much lately.

 

Is it a case of the thermostat being knackered or temp sensor perhaps? Seems these always show themselves to be at fault in winter, which makes sense. How much of a job is it to replace either of these if they are the problem?

 

I am hoping it's not a dead turbo, it feels fine when it's working properly. Pulls from 1500 and gets stronger up to 2000 then keeps going up to 3000+.

 

cheers all

 

Could be sticky vanes. Best to get your garage to check it out rather than guessing.

Sticking VNT mechanism on the turbo!

All is not lost search for 'mr muscle'

Already mr muscled it once...might give it another go though, it is much easier than faffing about with the sensors. It will also give me a good chance to clean the manifold.

JAse, I've been wondering if it is the VNT adjuster rod has gotten a bit sticky, I've heard they can get rusted and stuck as well as the vanes internally. Gonna give it a blast with some cleaner next time I am in there. 

Squirt a bit of penetrating fluid on the actuator rod and have a see if its free to move.

Be warned you will hurt your finger

heh, Yeah I learnt that the rod is quite stiff  when mr muscling it last time. Cheers.

Try sucking on the vacuum pipe while you have your finger on the actuator.  If it moves smoothly then I would think either the MAF or CTS was failing.

 

A stuck stat would cause your engine to take *forever* to warm up and you don't mention that.

 

The temp gauge on the dash is designed to show '90' within a certain temp range (say 85-95, for example), so if you see a variation, that would make me think the CTS is starting to fail.  As I am sure you know, it has 2 outputs - one set to the ECU and for the dash.

I must admit I know very little about the CTS mbames, I've seen people have problems but mine has always worked so it's never been something I've looked at. Going to give the turbo and intake a bloody good clean see what happens. I did recently replace (almost) all the vacuum piping. I'm not sure if it coincides with me changing that or not though tbh. 

Check that applying a vacuum to pipe from the n75 to the actuator on the turn makes the actuator arm move smoothly first.  That will indicate if the pipework is sound, and if the turbo is rusty/sticky.

 

A faulty CTS may generate a fault code (if really bad).  I tend to work on the fix-it order should be based upon the price (and ease) of fitting parts.