I have an idle question if somone has any ideas I would appreciate it.. When I first crank up my car it is in open loop and about 900RPM, after about 30sec it goes to closed and is at about 650RPM, then when I put it in drive it drops down to about 550RPM-600RPM. then if I put it back in park or neutral it doesn't go back to 650RPM, it jumps up to like 1000RPM.. Why is this... It stared a couple months ago.. Also right after I crank it, if I don't let it go into closed loop and I back out of the driveway, when I go from reverse to neutral to drive when it hits neutral it revs up to like 1200RPM then slams into drive... Any ideas, I was thinking maybe IAC or TPS sensor, but im not sure.... Thanks everyone.. its a 1988 transam 305TPI Auto trans... mods below.

 

could be that your IAC motor is getting old or is dirty -- causing slow response time when you first shift out of drive.

My TA does this as well but usually when you get it warmed up sufficiently it will not idle in any gear over 800 rpm.

have you checked your TPS setting??

could be time for a new O2 sensor (bad ones cause rich conditions which might lead to high idle)