Audi TT Engine Help

[Myosotis]

Hindsight is a wonderful thing and If I had it I wouldn't have started here!

2013 Audi TT 1.8 TFSI had major engine failure (at speed) took it to my local mechanic (very competent but not an Audi specialist), a broken valve spring and valve dropped. No apparent damage to bottom end/pistons/bores so replaced valves, springs, skimmed and pressure tested head, new timing chains (stretched) compression good, misfire on start up traced to blocked injector. So all good? - no After 10-15 minutes running it starts to misfire in mid range and fault codes show generic multiple misfire. But there is a solenoid valve which apparently pushes additional oil to the VVT system (?), when disconnected engine runs perfectly with no fault codes other than open circuit on the solenoid. Sorry all a bit vague but I don't have the codes etc in front of me.

1) Any general comments (other than I should have gone to main dealer or Audi specialist) on what the fault might be
2) Should I cut my losses and go for a recon engine at around £2k or run with the solenoid disconnected?
3) Throw myself on the mercy of an Audi dealer but presumably they wouldn't want to touch it or would want to redo work done so far

Any thoughts?

[E-bmw]

So, in other words, either the solenoid or the VVT is goosed.

Have you tried a new solenoid?

Alternatively have you called WBAC yet?

[Myosotis]

Sorry WBAC? Not tried a new solenoid yet but I'm sure we've all been there spending money chasing faults and costs are mounting up. Its the fact it runs OK with the solenoid disconnected that is throwing me a little.

[mtrehy]

Is it not under manufacturers warranty?

Even if not I would suggest contacting them as it's not heard of for things to be done as a goodwill gesture. I had a complete cylinder head on an old Renault van done F.O.C a few years back. You need to contact the manufacturer not the dealerships.

[stevieturbo]

Buy a known good used engine complete with injectors.

It would be rare for an engine that has dropped valves not to have damaged pistons....and in the case of a direct injection could easily have screwed 1 or more injectors too.
Especially as you say it happened at speed.

[E-bmw]

Myosotis said:

Sorry WBAC? Not tried a new solenoid yet but I'm sure we've all been there spending money chasing faults and costs are mounting up. Its the fact it runs OK with the solenoid disconnected that is throwing me a little.

We Buy Any Car.

[Myosotis]

Sorry quick update, I didn't realise it but the mechanic has already replaced the VVT Solenoid with a new one so we have to assume that's working OK Any more thoughts?

[E-bmw]

We need to know what the SOV actually supplies oil to/for then, as that looks like the issue may be down that line at a guess.

[Elliot2000]

The vvt solenoid must be feeding the cam hub, with it disconnected it isn’t feeding pressure to the hub so will sit on its rest point, which I think is in retarded position. When it’s plugged in and decides to feed pressure it will advance the timing. You have possibly got a problem with the hub not moving into position as it should or possibly when the timing was all setup during rebuild- the hub was not locked into its end stop so then moved further into the wrong position when activated by the solenoid.

I’d want to recheck the timing setup and also confirm the hub is fully retarded when engine is switched off


Also, potentially, by unplugging the vvt solenoid and disabling the vvt system, it may disable other systems or engine modes - for example - lean burn mode.

Edited by Elliot2000 on Friday 9th March 15:26

[Myosotis]

Thanks Elliot, Mechanic is currently dismantling his previous work, including timing set up to check everythng he has done is correct. I will pass message on checking the hub movement.

[Myosotis]

Hi Elliot, following up on your advice I've watched some stuff on youtube etc. there seem to be two elements to the VVT, firstly the hub which effectively varies the timing of the whole camshaft which is operated by oil pressure (which is what I believe you are suggesting may be at fault). But I also see there is a moveable cam which runs on splines on the camshaft, effectively moving a different profile cam onto the cam follower. Just for my education does the 1.8 TFSI have both of these systems? if so what drives the cam change mechanism is that hydraulic or electrically actuated?

[Elliot2000]

It sounds like you are describing variable valve lift mechanism, a separate system to vvt altogether, I’m unaware of Audi/vag having this setup, but I’m not sure. But bmw have valvetronic which is this system, and it is controlled by an electric motor. In bmw’s If you disconnect vvt then valvetronic also ceases to work - Audi may have similar setup.

[Myosotis]

Just in case anybody is interested, and thanks to those who offered advice. Problem was eventually tracked to the VVT hub which was "jammed" therefore not advancing the VVT even when the solenoid was passing oil to it hence misfire at around 3000rpm. Hub dismantled cleaned and reset. Seems to have fixed problem so (touch wood) now running sweetly. Total cost around £2500 parts and labour inc VAT for new valves/springs, head skim and test, new timing chains, new injector,VVT Solenoid and diagnostics, oil, gaskets etc Could have done without spending it but less than I thought it might cost.