Detonation? Misfire? need some advice if possible.

[Bane]

Not quite sure if this is detonation or something else...

was driving along this morning gave it WOT while already at 100-110kph while at 2nd stage boost of 15psi, felt like a momentary loss of power, a sound sort of like a deep BOV release and giant black puff came out the exhaust. not grey, not white, not blue.

is that detonation? there was no backfire or anything that sounded like the stuff in movies ie. kaboom

From a standstill i attempted to recreate the problem and could not... i am not going to keep trying this obviously. I've set it back to 1st stage boost at 10psi, and everything is smooth.

soo my question is...

What causes detonation, if that is indeed what this is?
If anyone thinks it's not... best guess at what might have happened?

vf34 and intercooler have been on for 4 months, and roughly 22-24,000km.

Have also been experiencing an odd hesititation in the last month or so where the engine seems to "miss" when accelerating at about 1/2 - 2/3rd's of the way down on the accelerator, at a specfic RPM, and speed range, which was pretty much where this happened. People had suggested that it may be electrical. I cleaned the air filter just to be sure (which was in fact filthy). Since cleaning the air filter, i find the car seems smoother during acceleration, but almost like it's lacking in power at WOT (like the torque isn't what it used to be?)... but thought it was me really just getting bored with the higher boost.

This^^ problem has been getting more noticeable as time passes.

I also had to replace the battery that same weekend.

cleaning the air filter did not fix the "miss". Could this be related?

don't know if that last bit is relevant or not, but i thought i'd mention it.

on the N/A engine, the car belching smoke didn't really bother me much, because it was just dirt coming out.

however in the turbo engine, i'm nervous as i have no idea what this could do to the turbo.

if the spark didn't fire off, then what? gas spins past the turbo and hits the hot catalytic and combusts?

are there any easy things to check?
i sprayed water on the wires earlier but had no broken arcs or anything like that?
would fouled plugs cause something like this?
or maybe a bad ignitor?

Any all suggestions are appreciated.

someone on another board suggested cleaning the maf sensor with electrical contact cleaner... but i'm really wondering about spark and coil pack.

[Imprezive]

When was the last time you did a general maintanence update? Check your plugs, plug wires, connections, oil, and so on...

The fact that you puffed a bunch of smoke out makes me think misfire, but i dont know. Just try eleminating any and everything that might cause the problem. Make sure you hit all the obvious spots and don't leave stuff out because it seems "to simple" ----Ive done that before and I felt like a dumbass....

[Bane]

lol, yeah... been there before

everything with the exception of the plugs and wires have been checked, though the plugs were supposed to have been done at the last service.

2 weeks before the turbo and intercooler upgrade, i had a $1700 service done at Subaru. 96k, 48k, boots and belts etc,etc replaced and repaired.

I'm going to bring it back and see if they'll do a diagnostics, i'd just like to have some background ideas to point them in the direction... or see if anyone else has experienced similar.

[Bane]

do our OBD I computers remember CEL codes?

I have seen the light trip and then disappear within 10 seconds, and this has happened usually at high sustained acceleration at high speeds, but it isn't easily recreatable.

I'd be a little frustrated if i paid for an electrical diagnostic, and it doesn't remember these things

[Threshld1]

Yes it will retain any thrown codes. Im not sure if your aware of this but you can check the codes yourself for free

[Legacy777]

I'd suspect a missfire as well from what you described.

Detonation causes audiable noise. Pre-ignition typically doesn't, but pre-igntion typically kills motors very fast.

And yes, check the codes and see what has been left.

[subytech]

I would suspect missfire as well, your obviously getting fuel (big puff of smoke) and like Legacy777 said you would hear detonation, and if you had either detonation or preignition i dont think you would have that smoke. And I dont know about the shop you use but at the dealership i work at we only replace wires if they go bad (not my personal philosophy, I just follow the rules). So i would check the plugs(just to be safe) wires and then look at the coil/ignitor.

[Bane]

okay to update:
Yesterday i had the hood up, and the turbo also appears to have gotten noisy now, just on idle with the hood open i can hear it, almost sounds like it's vibrating? Could just me being overly cautious, as i find that sometimes it seems like the whole exhaust system is louder on somedays more then others.

which come to mention it, it seems to be louder in general since this happened.

Wires were apparantely done about 6 months before i bought the car last summer. Set of NGK wires.

I was told plugs were done at last service.

As i had indicated there was a noise when this happened, just not the one that's typically associated (everyone says pinging?) it was a deep woosh noise, sort of like a BOV venting.

thanks for all the suggestions guys, i haven't been able to check this stuff yet, but i will be having the electrical system checked on Monday probably... sooner if i can find a shop i trust.

[Imprezive]

Check the plugs, dont trust what anyone else has said until you know for sure. What have you got to lose?

Thats weird that your turbo is making noise, check the heatshields maybe?

You can check the ECU error codes very easily, consult this link: http://www.surrealmirage.com/subaru/subaru.html

Let us know your findings