Coming off slip road, put foot down momentarily, loud clunk/bang, then running very rough with lots of smoke coming out the back!!!!!
Engine does start and run, but very rough.
Diesel put in tank some weeks ago by mistake(10 quid), unfortunately couldn't drain it at the time so filled it right up with Optimax and drove it carefully until a few tanks went through it.
Do you guys think this is the cause?
Car is my93 WRX, full decat, filter, ScoobyEcu, HKS SSQ, running a relatively safe 1 bar (was running!!)

Have you guys got any idea as to what's happened, any advice appreciated

 

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Doesn't sound too good! I'd probably take all the plugs out and see if one is contaminated more than the others. This should at least point to a cylinder specific problem or a more general one. Does the oil and water look ok (not mixed)?

 

Don't think it's the h/gasket as the oil and water don't look mixed at all. There is a lot of pressure coming out of the oil cap, but I'll try the spark plugs too, what do I look for there, pressure??

 

Oil ! .

Could be a holed piston : eek: , in which case one plug will probably be more oiled than the rest. Or may just be a gasket/seal somewhere, in which case all 4 will prob be oily.
I'm no expert though, so don't get depressed yet! I've had a holed piston however, so know the nasty noise it makes!