when cold, idle drops when shifting from "P" to "R" or "D"

when the motor is cold and i shift from park to drive or reverse the idle drops to about 200 rpm and the car shakes violently until i hit the gas. After driving for a while it seems to get better. my car idles at about 500rpm when i’m stopped and on “D.” What’s the cause of this?

My car is a 1991 2dr automatic it has a 1998 B18B motor w/60k miles, body has 217,000 miles, new starter (rebuilt), new plugs (NGK), new main fuel relay (OEM).

Again this problem happened just recently, i’ve had the motor installed 2 years ago, and this is the first sign of any problems.

from a VERY random idea standpoint, if you put it into those positions, it will engage the transmission, and I have always seen automatics (I don’t drive many… so this may be wrong) drop a little, so maybe your’s “engages the clutch” (I don’t know how automatics work, but I think you get the idea from that) too much instead of keeping it off till you hit the gas? just an idea, if there’s a setting for that.

yea, i agree, but recently the rpm started dropping lower and lower, to about 200 rpm, and it feels like it’s about to die.

how cold ?

do you let the car warm up enough?

this is normal

Also- there is no reason to hold the car on D or R unnecessariliy when not driving.

i’m here in so. cali. so it doesn’t get terribly cold, mid 50’s at most. I let the car warm up a good 2-3 minutes. It’s strange cause it never acted like this before. Should i do the FITV and IACV cleaning? or do these two parts have nothing to do with what i’m describing.