by Sheik Jabooti » Fri Nov 09, 2012 6:18 pm
*****************FINALLY SOLVED AND FIXED*************************
So after months of chasing this one, Matt from Kido Tuning solved it in 5 minutes. It turned out to be exactly his guess - WasteGate chatter. Here is his expert explanation for anyone who has a similar issue:
Quote Matt:
"It was a combination of the intake AVCS causing lean spool, which generates a lot of exhaust heat(shown in the front O2 sensor resistance) in an attempt to get the engine spooled faster(yet mine spooled faster without it ) and that heat was pushing on the wastegate flap and making it chatter against the turbo."
"WG chatter is the cause, hence why it only occurred at one point and why fuel or timing would not affect it When I pulled timing, it made it worse as it made more heat(more unburnt fuel in exhaust) and in the same breath, more fuel made it worse as it was again, more fuel in the exhaust. So can be diagnosed as a weak WG actuator which is why the mechanics could not hear the knock"
Started with a Gen2 Outback, then got a MY07 GT Spec.B Manual w Cat Back Exhaust and Verso Tuned, now got 2 kids and a MY07 GT Auto Wagon, Ultrex stealth back exhaust, panel filter, Whiteline Sways all round, Spec.b struts and springs and Kido-Tuned.