Well this is puzzling me now.
Had the same mechanic who diagnosed it as having piston slap look over it again as he said when i pulled off it sounded like it was misfiring, but it still sounds exactly like piston slap.
I know scoobys sound like their idling rough due to the boxer engine so my mechanic whipped out his timing light and found the right bank are both misfiring, No 2 + 4 cylinders (i think)

Both cylinders are misfiring at idle, if you rev it to around 2,500 to 3,000 rpm the misfiring gets bad, but at 3,500 to 4,000rpm no2 cylinder does'nt fire at all!!!
We swopped the HT leads around and it still does it, maybe the plug gaps are too big or small maybe its the coilpack.
The thing is this so called Subaru dealer were supposed to give the car a multipoint check before it goes on sale obviously they did'nt or did'nt do it all just change the oil + filter.

I've done a search on here and i think its called bore wash ?!?
Where the petrols still being squirted in but no spark so it has to go somewhere either out of the exhaust valve or which is think it has, past the piston and contaminated the oil.

My tappets have got considerably louder over the past 4 weeks i've had it and i've had to top it up with 3/4 litre of oil, perhaps its the petrol in the oil is giving a false reading on the dipstick ???

Anyway its going in next Thursday for some 'investigation' work but before then can anyone help/advise me as to whats the hells going on with my car.

Any help is very much appreciated, i'm desperate as i'm seriously considering rejecting the car
Thanks

 

Ready to be flamed here but are you sure the tappet noise isn't your injectors? Mine are very noisy.

As for the knocking noise, mine (MY99) seems to have it too. It seems to come from the back right of the engine as you look at it. I have heard it to a lesser degree on a mates car but i'm still clueless as to what it is. For what its worth, it uses no oil so I doubt we have the same problem.

Good luck mate, keep us informed.

 

Thanks mate, it maybe the injectors we'll see what subaru say.
I'm sure but not 100% on a search i've done looking for piston slap, if its a knocking noise from the right handside of the car it maybe the cambelt pretensioner which if it is needs replacing asap
Try a search just to clarify

 

Don't know where you got that idea. Earlier PPP's used to use a Ramair filter, but the '99 one doesn't, and none of these packs has ever included the ITG.

It should have the Subaru paper filter in it. The ITG is known to give the MAF sensor (particularly the type used on 99/00's) a very hard time, and using one will instantly invalidate your warranty in many cases. Take it out!

 

A VTA BOV on a MAF based fueling system (the Impreza as standard) will almost certainly cause Bore Wash - hence why a lot of people don't recommend them, and also why some people have suggested that you replace the standard BOV. It's unlikely to be the cause of your problem if you only fitted the VTA BOV after you got the car, but it's an easy get out clause for IM.

Matt.

 

Don't worry all back to standard now, cheers chaps