Every now and again my 86 Max will start doing some weird stuff at idle... It used to be after I heated it up a lot(hard driving) shut it off, and then started it back up, or went to, it wouldn't always start first try, it'd grind and register no oil pressure so I'd wait a second and try it again and it'd work, but when I came to a stop the idle would fluctuate like the car wanted to stall, well yesterday, after some mild driving(105mph on the highway for a little while) and crusing around for about an hour I came home and shut it off, then when I went to leave for work, erratic idle, stall 3 or 4 times before I could get it running smooth enough to trust to drive it somewhere and the idle has been a little erratic since. Anyone have any ideas? I know I'm due for a coolant flush&fill and oil change, which I'll be taking care of Monday(work at night instead of usual day) but I'm worried it may be something a little more costly like starter or TPS or something of that nature, there is a small crack in my exhaust before one of the cats, would that affect my idle at all? Any input would be appreciated