So I fetched my 600K mile Caddy from OK a little less than a year ago. Father had been driving it while he put the 1.9 in the 82 Caddy. It'd had a case of worn injector nozzles for awhile and not driven a lot in the year or so he'd had it. He stuck in new nozzles but did not have them balanced. Idle was a little off but it was not bad on the highway.
So I'm driving back to NC and in a slow crawl traffic jam in TN there is suddenly a loud metalic bang bang bang at about crank speed. I figured the worst, got off the interstate and said a lot of bad words. In ten minutes or so, I quit. Just went back to more or less normal. I proceded the 500 miles or more home without incident.
Fast foreward 6-8 thousand miles and many months. Daily driving still, not much smoke, cold starts OK, no oil usage really, MPG is about 38 which is low but this engine probibly has 400K or real close on it so I can swallow that. Trouble is this. At higher RPM's, such as the top of each gear before shifting, there is a rattle. It sounds like it's about half crank speed but I could be wrong, and it falls off over a period of a second or three if you life off the throttle. It's like if you had a pebble in a can and slowly started shakeing the can fast and faster as RPM increases, and slower as it drops off. I can't duplicate it sitting still, but if I"m rolling and clutch in I can rev it up and hear it. Other than the kinda off idle that tends to run up and down a couple hundred RPM now and then, it runs well, starts well, smokes not much, just generaly feels like a high mileage 1.6na diesel.
I'm thinking valvetrain, and that the brief clanking noise was a piece of carbon maybe that came loose and beat around in there and possibly tweaked a valve. I'm working on another car and just hopeing this old critter hangs on for a bit longer. I thought I'd ask if this noise sounded familier to anyone. Thanks..