Son's 4runner again has started to have an intermittent miss. He did the tissue paper at the exhaust pipe and maybe once every 5 seconds it will suck back the tissue. To me it sounds like a sticking valve? He drives it maybe 30 miles a week since the transit train is only 5 mins back and forth from his place. I said, put in some (2CUPS) Marvel M Oil and run it for a week to see if it clears up. It has had the heads done 2yrs ago and symptoms came up quickly, like in the past two days.
any input would be appreciated.
BMJ

 

Burnt valve, tight exhaust clearance, sticking lifter. Do a compression test and report back