RRocket

I have a simple question. From a cold start until the car is warmed up (ie Normal Operating Temperature)..anybody know what that number is? How many degrees constitutes normal operating temperature until the enrichment circuit is closed?

VVTiBob

Not sure if this is what you’re asking about, but generally speaking normal operating temperature for Lexus/Toyota engines is approximately 190° +/- 5° but can range up to 220°. Obviously there are many many variables that affect performance and temperature. But we would be getting deep into the weeds of ECM programming, e.g. fuel trim itself and fuel air ratios as measured from multiple sensor inputs (O2, MAF, ECT etc etc) to the ECM.

VVTiBob

For more understanding on fuel trim issues consider this video......

RRocket

I hooked up the ODB real time reader. In the mid-30s outside temp, the coolant temp hits 182 and stays there more or less.

So that's pretty close to your number.

VVTiBob

Yep, sound correct. The few degree difference could be a failing ECT sensor. The only way to know is to test and check calibration. Here’s a link to the ECT sensor location: https://www.clublexus.com/forums/att...on-sensors.pdf

VVTiBob

If your concern about Engine temperature and how it affects fuel trim then yes, you should check the ECT for correct/proper calibration/readings.

Lavrishevo

iTrader: (1)

I replaced this sensor on my LS430 I want to say within the first year of ownership and around the 100k mile mark. It made a notable difference in fuel economy. I have been planning on doing the same with my SC. It is interesting how the temp guage for the cluster is a totally different sensor. Probably worth doing as preventive maintenance every 10 years.