and that something was the oil. well i did but not well enough, i bought with it sounding kinda of rattly under the hood. figured it needed a valve adjustment or sticky lifter. the noise was more apparent in the cab then under the hood. i just checked the oil and it looks bone dry. i added 4 1/2 quarts of oil in there (10w-30) quieted it down drastically. has good oil pressure per gauge about 32 idle and above 40 psi when accelerating. no more rattling sound when driving, but there is a taping sound at idle. not a deep knock but more of a solid tap, does not become louder as rpms go up, actually it pretty much disappears.
im pretty sure its not rod knock as that usually gets louder as the rpms increase and i have heard rod knock before.
possibly the flex plate bolts? but the noise goes faint as i rev.
If it goes faint/away when revving it would be your flex plate bolts. I bought a jeep for $700 same as you described, and tightened the bolts with blue locktite, never made a peep again.
7th jeep.Purchased bone stock on 3/05/13. Dark Red 2000 XJ. Automatic, 6.5inch Rough Country Long arms. 33x12.50x15 KM2s.
To be installed, grand cherokee alternator, durango steering box, currie steering. Then lockers
Out of the exhaust. It ran clean when I was checking it put though, I'm going to run some 10-40 when I change the oil later this week. the smoke is not bunch, can't see it when driving.
Give the exhaust a light sniff to see if you smells sweet light antifreeze.(Obvious do not massive inhale the exhaust, durrr.) Check your coolant level to see if it drops over time. This would indicate a leaking head gasket.
On older engines the valve stem seals leak letting oil drip down into the combustion chamber. Replacing these are fairly easy to do without removing the head.
maybe it didnt smoke because it had no oil when you looked
This could unfortunately be the case
Had a nissan that would smoke like a freighttrain. Id just look out the mirror every once in a while when driving, and when it wasnt smoking it was time to pull over and add oil.