Stalling & poor idle while in D

[jonah111]

I'm really hoping to get some advice on an issue with my sisters car that I've been trying to fix off & on for the last six months. The car is a 97 850 NA and it's having issues idiling while in drive.

The car starts up and drives fine for the first couple minutes. Within a couple miles after warming up, the idle will fluctuate between 400 & 1000 rpm at a stop light and it will eventually stall after a few seconds. If I shift into R, N, or P the idle immediately pops back up to a solid 1000 rpm. It's usually about this time that the check engine light comes on with a P1507 code. After stalling, the car starts right back up and idles fine in Park. According to my sister, it seems worse in warm weather.

What I've done so far:

Replaced IAC motor twice
Swapped MAF with my 850R
Replaced spark plugs
Checked for vacuum leaks

Last night I drove it with the ECT unplugged and it seemed to run fine (other than the fan running constantly) and idle stayed around 1000, so I installed a new sensor today. Still having the same issues. Another thing I noticed is that the temp gauge only goes up about 1/3 of the way rather than 1/2 way. I was going to replace the tstat along with the ECT, but the torx screw was stripped.

Could this be an issue with the torque converter since it only ocurrs in Drive? I noticed tonight that as the idle dropped around 400rpm, the orange arrow on the dash would light up.

I'd appreciate ANY advice on what to try or check next.

thanks!

[Ozark Lee]

It sounds ECT related but you may need to get deeper into the weeds with the wiring back to the ECU. Cleaning the edge connectors on the ECU itself might be a place to start.

...Lee