2.0T hesitation/power loss

[ALF_A4]

My 2.0T engine has always felt good for the full complement of horses and very smooth (for a 4-pot turbo, anyway!). Until this week, that is. I noticed a slight hesitation in the mid range for a few days, then on Monday on a long drive it very noticeably lost power on anything except a small throttle opening. As you open the throttle more it hesitates slightly, then accelerates right through the rev range but much more slowly than normal. On a part throttle and at idle it feels exactly the same as before, economy is the same, and there are no warning lights on. I recall something commonly fails on these engines, what was it and does this sound like the issue?

Also the car is only 2k miles from the next variable service, and has done 72k overall, so I've booked it in for a service and to look at this next week (independent VAG specialist I usually use). I'm going to get the cambelt done, and the water pump, is there anything else that is recommended at this time besides the water pump?

Thanks!

[bez101]

1st off id get it scanned for codes common faults on the 2.0t are CTS MAF N75 it could be down to your fuel and a few more things
for the service just go for the belts waterpump fluids and all filters also the fuel filter

[ALF_A4]

Cheers. I do a lot of miles and have already been through the tank of fuel I had when the problem started, and well into another, without improvement. I run it on Super. I hadn't thought about the fuel filter - will definitely get it done!

Edited to add - right, I'm now a lot less optimistic than I was - it seems to be using oil (not a lot, but noticeably) which it never has before, and one of the exhausts has some oily black muck in the bottom of it...

[Lateknight]

I was going to say this sounded a bit like the turbo recirculation valve (N249) as from the factory they fitted a rather flimsy rubber diaphragm version, which has been known to leak after a while. Latest version has a plastic skirt which is a lot more durable. Would you say its like you are losing boost?
Then I read your sooty exhaust comment. Whats your fuel consumption like? Could be air mass meter (G70), as Bez mentioned. Could be Engine temp. sender (G62), if your fuel consumption is a little high.
Does it sound like a misfire?, as coilpacks are not uncommon.
Poor running can also be caused by loss of high fuel pressure. These engine rely on a fairly hefty fuel pressure -for a petrol engine- to be supplied from the mechanical lift pump to operate efficiently. Any drop in pressure can also cause running problems. This is usually caused by a worn pump or a worn (or damaged) pump cam follower. Again something that is known to the 2.0T engine.
Hope that helps (a little)

[ALF_A4]

I do a lot of miles so mpg is easy to notice - and it is doing exactly the same as before (indicated range 500 miles-ish). It feels exactly as before too in all instances except when requiring half or more thottle. It starts and idles fine, revs cleanly from idle, is totally smooth when driving (no misfires or anything like that). And it will rev. If you only drive it on a tiny throttle opening, you'd never know anything was amiss, it feels as keen as ever.

Then you go for more throttle and for a split second it picks up, then changes it's mind and accelerates steadily but much more slowly than usual. Particularly noticeable in higher gears from about 2500rpm. It is exactly like I'm losing boost - like it is starting to build, then letting off.

It's going in this Friday now - I do a lot of miles for my work and really hope it is fixed quickly, and is not too expensive - I just spent nigh-on £700 on tyres and it also needs a service and cambelt change! I was thinking - I have never before had an engine-related reliability issue on any of my cars, in around 18 years/400k miles of driving. If you excuse an occasional glitch on my only other German car, a Passat V6 Syncro, that sometimes lost power and needed re-starting. And that includes 150k miles in V6 Alfas... And about 6k+ track miles testing/track days/racing with a Caterham with a K-series engine!

[ALF_A4]

According to the garage, from the fault codes and so on they suspect the turbo needs changing. ****. It seems a bit odd to me that the car would go from feeling fine and not using a drop of oil to suddenly losing power and using oil, but I suppose something within the turbo probably failed at that time. Apparently it's fine to drive for the time being (albeit not having much acceleration), I'll get the turbo replaced when on holiday in a couple of weeks...

Edited to add: picked it up, the bill was £700 for the service, cambelt change, and water pump, which was exactly my guestimate. Turbo is likely to be £1000+ which makes a total of £2500 ish with the tyres I just bought as well...

The guy there (a fairly large VAG specialist) said they do a turbo a week on VAG cars, often as young as mine or less, and no obvious patterns in terms of petrol vs diesel or longlife vs normal servicing. He said the non-VAG stuff they do, especially Japanese cars, seem to get through turbos a lot less...

Also, when I got back I did the classic "idle for a few minutes then get someone to boot it at idle while looking at the exhaust" check, typical of checking if a turbo is on the way out, and despite the prescence of oil muck in the exhaust and some oil use since this problem started there is no visible smoke at all then, or when driving. And it feels much better at high revs than in the mid-range. Odd.

[Sloppy]

Sounds strange to me when turbos literalyy fail they often just go bang and you really notice them.

As discussed abvoe the turbo valve fails alot, my car felt a bit slow after i got it, after reading a few forums i was so convinced it was a booost leak i went and got one from audi (£45 + vat) and sure enough when i swapped it the old one had 2 big rips in where it had been losing boost.

New one on good as new!

Its certainly worth a try before a fewk on a new turbo!

[Lateknight]

Turbos can wear, but generally with visible clues first.

I agree with the above, get the recirculation valve checked first.
You'll need the car on a lift or ramps as its only really accessible from below.
Undertray off. Look up to front of the engine on the front of the turbo, there is a black plastic housing held on by 3 allen-key-head screws (chrome coloured). Thats your baby you need to unbolt. Nothing else will fall out once unbolted! Obviously mind it might be very warm in that area if the car has just been run. Here's a (rather 5h1tt) picture of the item in situ. Your looking for the N249 Diverter / Recirculation valve.
http://img.photobucket.com/albums/v4...am00/turbo.jpg

Here are piccies of the old type and new; (old on the left, new on the ....)
http://www.my-gti.com/wp-content/upl...06h145710d.jpg

Current modified part number 06H145710D (about £45-£50)

[ALF_A4]

Thanks - my father in law has a car pit in his garage (handy when I used to race, especially the Hayabusa engined car as that was a nail). I'll get it in there this weekend and check this part, as I have 2 weeks until it is booked in for the new turbo and I need to find out if it needs it in the meantime!

[ALF_A4]

Turbo diverter valve being changed tomorrow. The part number above only seems to bring up American parts sites in Google but was enough for them to order it here... Here's hoping it fixes it!

Edited to add: It did! The old one had a split in it. Now it will be interesting to see if the slight oil use that started when the diverter valve began playing up was related or not. Apparently it also shocks the turbo somewhat when the valve is knackered so it will be interesting to see how that goes as well... I deliberately kept throttle openings minimal while it was sick.