Rough idle in drive
 

I just picked up a '91 240sx today and have some minor bugs to work out. The first item on the list is a rough idle when in drive (automatic). The engine idles fine in neutral or park, and it drives great once I'm moving, but when I come to a stop the rpm drops to ~600 and it vibrates enough to cause the hood to shake. It doesn't really sound like it is missing either.

The car just passed CA smog as well, although the idle Hydrocarbons were on the upper range (86 with an allowable 120). All the other numbers were at or below average.


Distributor cap, rotor, plug wires, and plugs are new. Oil was recently changed. Not sure how old the O2 sensor is, but like I said it doesn't seem to be missing. Maybe bad motor mounts? I'll get a better look tomorrow when its light out...


Also, how often do the timing chains need to be replaced?



Other items on the list:
leaky ps hose at reservoir
Torn steering rack boots
front suspension clunk sometimes when turning
"soggy cardboard" rear spoiler
power antenna tries to retract when I turn off car, but just makes noise
torn front seats (rest of interior is immaculate)
dents on all driver's side panels (previous owner learned about black ice the hard way)
cracked front windshield
paint


Hopefully I can tackle those one at a time over the next year and a half while still in college. Once I'm out (if I still like the car as much as I do now) I will probably swap some CARB legal turbocharged engine/manual transmission in (no SR for me, maybe 3s-gte, 7mgte, or 2jzgte), do coilovers, bushings, and LSD.

Anyway, thanks to anyone who listened to my rambling. I would appreciate any help at all with any of the problems.