My 85 Jetta GL Auto AC ~200,000 miles started sounding like metal popcorn under acceleration a couple months ago. So far, I've: replaced the (missing) transfer pump and replaced the fuel filter. I've checked: the oxygen sensor the coolant temperature sensor the differential pressure regulator the air flow sensor plate the vacuum ignition advance the mechanical ignition advance. All are within the specifications in my trusted Bentley manual. Following the Bentley procedure, I adjusted the idle to 900 rpm and set the timing to TDC. It still pings.
I'm running 91 RON gas from a Costco station here in Anchorage.
Any ideas? mailto: snipped-for-privacy@acsalaska.net