Remove and Replace ECTS:
The OEM ECTS was a mostly plastic device that is installed into the hot coolant stream in the engine. The plastic immersed into the coolant would quickly crack, that would end up causing the high idle symptom, and excessive fuel usage. There’s an easy check for this. That’s to remove the connector from the end of the sensor and look for green corrosion on the terminals. I did that and yes, I did have a small amount of green. So ordered a new brass ECTS from Amazon. Only $12 or so. The ECTS is mounted into the end of the engine on the drivers side. You only need loosen the plastic air breather tube, swing it up out of the way to give access, as shown in this picture. If you have excessive green corrosion on the connector, you can buy the connector with 6″ leads for around $12 too. Cut the old one off, solder and heat shrink the new one on. Because of the grime in that area of the engine that most owners expirience, soldering and heat shrink is recommended.
Next, jacked up the drivers side of the car 6″ or so, and then loosened the radiator cap to relieve pressure from the cooling system, then retighten it. That reduces the amount of coolant that will leak out of the ECTS mounting hole when it’s removed.
Than, using needle nose pliers, squeeze the connector a bit and remove it from the ECTS. Check the inside for corrosion. If badly corroded, buy new or find a Saturn in a junkyard and pull the connector from a different part of the engine, along with six inches of wire. Snip off the old connector and splice, solder, and shrink tube on the clean connector.
And here my deep socket is over the ECTS ready to remove. Center of picture just to the right of the large rubber hose. After it had been removed, only a couple tablespoons of coolant were lost.
And here’s a shot with it installed and the electrical connector reattached.
Here’s a comparison between what a good and bad ECTS looks like. Thanks to Mike Thompson dot com.
https://mike-thomson.com/blog/wp-content/uploads/2012/07/ects-old-vs-new.jpg
The nose of my ECTS was plastic, and indeed cracked. Not as badly as some of the stories I’d read indicate happens, but enough that some coolant has seeped out and contaminated the connector a tiny bit. Which accounted for the small amount of green corrosion on the terminals. Here you can see mine was slightly cracked so it wasn’t as bad as some, but definitely needed replacement.
Replaced the ECTS, and because I only had a little corrosion, used contact spray and buffed the connectors, than reattached. After that, reattached the air intake tube, added a bit of water to the coolant reservoir, and off I went to test. When I did this job, the SES light had been on more than off. Just afterward, it went off and stayed off for a couple three weeks. Before this replacement, the idle could be called, flakey. One time it would be normal at 750 RPM, next time it would be hanging at 1200 RPM. And my mileage didn’t really change much. Still only 22-24 MPG. Hmmm…so, more to do.