My '95 1.6L DOHC has ok power and gets ok mileage still, but just started making a deep (and fairly subtle) thumping noise through the air filter. It sounds to me sorta like I'm getting some exhaust blow-by back into the throttle body. Does that make any sense? Cylinder #1 has a noisy HLA that quiets down quickly if I switch the ignition off and then restart (it only clatters at startup.) Can anyone suggest a cause or fix for the thumping noise? I've already got "new engine" checked off on the list, but I'd rather not go there right now.
Thanks,
Darren