Is this a blown apex seal, or some wacked vac leak?
 

Hi! I was driving today, and suddenly the car started acting up on me, like an intake hose or something popped off, getting really rich fuel mixture, and loads of backfire.

The engine is an S5 TII, afaik, it got under or just above 60k miles on it, which is supposed to be nothing, even on a rotary.

However, I checked all the intake piping, from the airflow meter to the throttle body, everything is as it should, tried with pressure, so there are no leaks there.

The car won't idle, and I have had vac leaks before, like small ones, and the car only got a bit rough then, but this is totally different, seems like limp mode as I remember it from my Passat, but afaik, the FC engines doesn't have limp mode.

The airflow meter might be bad, the car idles just as bad with as without the airflow meter, but it might also mean nothing. I will try taking out the plugs tomorrow and crank the engine without the EGI fuse (I think that was the one, correct me if wrong), and see if I feel anything different on the different rotor faces.

Also, I wonder if it might be the wastegate actuator that is stuck in open position, keeping the wastegate open? I tried starting the engine with the intake all the way to the turbo off, and the turbo didn't spin, I don't know how much or if it should spin when running on the starter, but it should go around by the compression puffs from the engine? If the engine thinks the wastegate is closed, and since my pressure sensor is disconnected (I had the wrong one, waiting for new N370 this week), might this cause my problem?

But everything boils down to one of these:
Massive, hidden vacuum/intake piping leak
Airflow meter not working
Rotor apex seal blown
Wastegate stuck open
One of the ignition coils burned, or spark plugs dead, but only for one rotor, seems weird. Afaik, the engine should still work with one spark plug on one rotor, but I am not sure, need confirmation here.

I noticed that my boost gauge is going all over, jumping up and down all the time. I think that might be from loss of compression on two faces, but I am not too familiar with rotaries, so I can't say anything more than this.

Compression test woulda saved you all that typing.

It is 04:41 AM here now, can't start screwing around in a neighborhood full of kids untill morning.

Say that the compression test is ok, what would be your guess then?

If it isn't okay, it is also obvious what happened.

well it could be a 1000 things or just 1 but alittle background would help not just was driving today and lost power. details how do you drive it on a normal basis, how much boost you pushing, how were you driving it when this happened, did you physically inspect piping and turbo parts is the motor stock what intercooler. you get the point help us out we will help you out

personally sounds like you have a massive vac leak like and inter cooler hose blew or split

As I said, I checked the intake piping from turbo all the way thru the I/C and into the throttle body, seems good enough. Also tried to start the car without AFM and any piping, that is, pure air straight into the throttle body, no piping. Sounded the same as without. Didn't start, but it rarely does after this event.

I drive.. spirited? But rarely exceed the speed limit of 80 km/h (50mph), boost is maxed on 0.6bar (math sucks), I get 15-22mpg on city driving, some highway, some high acceleration and boost. I never strain the drivetrain and engine with burning/drifting and stuff like that, I always gear on 7k, I have had it on the 8k rev limit 10 times in one year maximum.

However, mostly, when I use the car, I only go full throttle to not get hit by any cars where I have to give way, going on the main road and so, else I drive like it like any other car, normal throttle, gear @ 3k if cold, 4-5k if warm, always let the turbo and engine cool down a minute or two before shutting down (need turbotimer, tell me).

My spirited driving and regular driving might be split 30/70 percent-wise.

Engine is still 60k miles, or around that mark somewhere.

More than this, I can't give you, hard to describe yourself, try it.

It can't appear so suddenly if it is the first cat that is clogged? The one that is almost a part of the downpipe?

Oh, according to the FSM, it can be 7 different things. I mean, 7 different engine electrical systems that fail. How nice to know. Also, vac leak, apex seal, jammed wastegate, blown AFM.

Big list of stuff to check. Especially when I can't use the self diagnostics plug (S5 engine, S4 dash harness, the S5 diagnostics plug never found its way into my car, and I don't have a separate check engine light in my S4 dash anyways. If anyone can point which ECU wire to plug to earth, and which to put a 12V light bulb on, that would help alot, pulling error codes instead of twisting my and others brain for something speculative at best.

well by sounds of it doesnt sound like you have blown a seal to me id do a compression test on her or take the plugs out and listen should have 3 blow outs each rotor if not bad seal then after you do that let me know what the vertic is.

Yeah I will, just need to get the plugs out, my brother stole my plug key. But I will try later today ;)

Did you check to see if there are any codes popping up?

Can't check for error codes, got S4 plug and S5 motor, no check engine lamp.

BUT, I found the problem. It was the compression, sadly. Front rotor, low comp on all three sides, meaning either two apexes, or the side iron seal on the rotor is dead. Hoping for the last one, maybe my rotor housing is okay after all.

Did you check to see if there are any codes popping up?