Hey all - I've been looking for a rough temp the '82 kicks out of the cold idle enrich (and its 1k+ rpm idle). I've read its based on the CTS (front of intake manifold, near tstat) and O2 sensor temperature (manual states ~390F). I recently swapped out the thermostat for a 160F unit while also upgrading the CTS to the newer two wire unit instead of the coaxial style OEM wire. The car has a chunky aluminum radiator and along with the lower temp t-stat, I'm wondering if i have to be concerned of the car dropping in and out of cold coolant enrichment. So far, it seems to be working fine but colder days are ahead and I cannot find any info on this, even the shop manual which convolutes the temperature sensors on the car. I am reading a troubleshooting guide that states "at normal op temp, coolant sensor terminal should be less than 1000 ohms" - which I guess I can back calculate based on bench testing. Im also noting that it states at 60F, the resistance should be around 4114-4743 ohms but I believe that's incorrect. At room temp (80F), I'm getting closer to 2.1K ohms at room temp (70F), and about 5K ohms around 32F in an ice bath *Edit* its definitely possible that my ice bath is only getting to 50F or so, so the earlier 60F -> 4K may be correct. Guessing from these measurements that the "1000 ohms" occurs around 130-140F, but still do not know the exact trigger point for ecm dropping out of cold idle. I guess I could just wire in a potentiometer directly and slowly adjust until the air pump comes on... I might do this in the future if the car acts up and no one else has an answer.

For anyone in the future, if anyone is trying to decipher all the temperature sensors, the '82 has:

1. Electric fan switch - Passenger side head. Coaxial. Black plug. No ECU integration. Turns electric fan on and off.
2. Gauge coolant sender - driver side. Spade connector. No ECU integration. Wired to coolant temp gauge reading in cluster.
3. ECM Coolant Temp Sensor. Intake manifold, front of engine. Coaxial. White plug. Covered with a protector (if its still there). Integrated into ECU. Controls cold idle, overheat warnings.
4. Oil Temp Sensor. Right above oil filter. Spade connector. Longer than coolant sender, looks similar. Wired to oil temp gauge reading in cluster.

 

If I remember correctly, fast idle is controlled by a timer. It's a given number of seconds at startup calculated by the temp at start up.

My question is why did you go with the 160F thermostat? People do that so they would have that extra enrichment for more power with an updated PROM.

 

Strange - I understand the timer part but the idle must also be affected by coolant temps because it now idles normally post swapping sensor and connector to the newer version. The 160 was just because cooler engine bay temps are generally better for most components (other than the oil, piston rings, i know). The car still seems to warm up and sit right below the second bold temp line (200F?) where as it used to go a little past that previously. I MAY swap it to something slightly warmer if i smell rich exhaust or feel it runs a little worse...

 

Just a quick update for future crossfire cold idle troubleshooting. All is well after swapping the old coolant sensor.

Anecdotally, a 160 stat, OEM fan setup, and a chunky aluminum radiator will not overcool the system in my climate (~75F) to where the cold idle comes on/off. Car temp gauge sits at a little under 200 in traffic. Seems like 160F is high enough for it to leave cold idle.