2000 Outback 2.2 died on offramp of freeway. Started up shortly after with a loud knock which disappeared after starting and engine is quiet and smooth at idle. Give it a little gas and there's a knock at initial RPM increase and then when throttle is released, otherwise medium knock under throttle while parked.
The question is.........could it be the Oil Pump alone? If so, how can I diagnose for certain?
If not, how can I tell if it's the lower end or the upper end of the motor?
Any other things I should be looking for?
230K miles, new timing belt, head gaskets, resurfaced and tested heads last year.
Thanks for your help!!