I replaced my existing CTS with an oem unit on my '98.
The old one didnt look too bad.
At the same time I pulled the throttle body for cleaning since I read about it on this website. The throttle body was kind of a pain to remove since it has cooling hoses attached.
The car idles differently on warm up now, and it seems to glide nicer when lifting the throttle off to coast. But so far nothing dramatic for this (new to me) car since it has received pretty good care over it's life.

BTW, there was some kind of black liner, or coating brushed right around where the butterfly/throttle body opening meet. Something like a sealer or leak test done at the factory. What was that for? Anybody know?

 

Does the CTS deteriorate with mileage or age? I have a 93 LS400 with 80,000 miles - the idle seems high when cold and the throttle response isn't great. Is it worth trying a CTS or is it more likely to be ECU capacitors. I live in a cool damp climate - rarely over 70 degrees.

 

Both mileage and age! - a 20 year engine coolant temperature sensor needs to be replaced, it's only US$49 at Sewell Lexus or Lexus of South Atlanta Parts - I strongly prefer the real Toyota part for this critical sensor.

and 93 is a very common year for ECU capacitor failure, I would have that done as well, if it doesn't need it, it soon will! - and in the meantime, both the engine coolant temperature sensor replacement and the ECU caps replacement will result in better performance, better economy, and the ECU caps will additionally give nicer shifting! - Just make SURE you order the exact capacitors I have linked to in post #1 of the ECU capacitors thread, they are a very rare type, and it seems every ECU "rebuilder" gets this part wrong and the results are then disappointing (or disastrous)

 

I also broke the the plastic holder when swapping out my ECT - the connection seems to be tight without it and I haven't noticed any issues/problems...do I need to address this?

 

A couple of notes, in case they didn't get added by others later in the thread:

1) The sensor takes a 19mm deep socket. I didn't have that size in my regular set, but an impact socket (thicker walled) just barely fits in the area around the sensor.

2) I had quite a lot of coolant gush out of the hole. Your luck may vary.

Speaking of luck, I expected to have to clean my sensor but was instead greeted by a very clean one and: a) a broken clip on the green plug, b) a partially bare [green] wire, and c) the base of the sensor itself was nearly broken off! Score another one for the ham fistedness of whoever worked on the car previously... They must have tried to yank the thing out instead of unscrewing the sensor.

Looks like I need to pick up a new sensor, after all. Any idea if the wiring can be replaced along with the broken-clip plug? It disappears into a wrapped wiring loom and I'm guessing becomes part of the main harness at that point. I wrapped the bare wire in electrical tape, which might be all I can do. Yuck.

 

I hadn't read completely through this thread before attempting my ect sensor change as well as throttle body cleaning and blah blah whatever else I could get to while all the intake hoses were removed.

I also had a ton of coolant leak out, a few liters at least, and that was with the overflow tank cap removed. In hindsight I probably should've removed the cap and then put it back on before removing the sensor. My sensor was also EXTREMELY clean (looked as new as the brand new part I was replacing it with, with 79k on the clock). My only problem with this project was removing the intake hose from the throttle body. That mf'er was on there really tight. Oh and I totally had a mini ***** fit when my CEL came on after reconnecting everything. Well almost everything, save for my maf sensor harness

 

Ha, I've done the same thing two or three times. For some reason, that MAF connector is easy to overlook when hooking the air intake back in.

I have my new coolant temp sensor in place and received a new connector and pigtail yesterday, but I haven't started on cutting the old one out and splicing the new one in yet.

 

hi all,

how do i find out the part number for my 1993 LS400 water temp sensor?

 

I used Beck Arnley #158-0421, which is a match for your model as well. From there, you can always cross-check part numbers if you want a different brand.

 

ok cool

thank you

 

well got the #158-0421 water sensor..

acceleration has greatly improved..

fuel consumption got worse..


i took a look as the old sensor that was in the car and its a #89422-20010

mine is an australian delivered Lexus LS400 t2d2.
hense why it might be different from yours.
cheers for the help though..

so ive ordered one of them and will keep ya's posted..

oh and the original sensor was stuffed bad.. it was an off browny colour instead of bright green. heat got to it good..

 

ok update.. now extremely happy...

new sensor in.. #89422-20010

with the old sensor i got 300km to half a tank of fuel..

i put the sensor in friday night and went to sydney saturday.. so 400km round trip..
only used half a tank..

so she is now back at really good fuel economy again..

 

Thanks to this post, I just changed my coolant temp sensor a couple days ago in my 1992 LS400. I now get a whopping 20 mpg combined, from a 16 mpg average before and my car doesn't smell like it's running rich anymore. Thanks guys - best LS400 forum on the planet!!

 

Hi
I just changed the coolant sensor for the ECU on my '93 LS400 190k km. Wauw for a change.!!! At the same time I changed spark plugs and cables. What a difference!:
The Engine is running so smoothly now.
The speeder responce has improved greatly.
The sound is much more prosper when hitting the throttle.
At the same time, I got rid of a split second of engine stalling when easing the foot on the speeder or the Cruise control did this.
And then, of course, the fuel economy has improved with significantly 20-25% and that is not bad as I am living in Denmark and paying nearly 2$ a LITER gasoline.

Thanks for the good tread and advise:-)

 

been running for a bit now so thought just to touch base again..

on the old sensor i was lucky to see 400km to the tank of fuel..

replaced sensor with the wrong type. ran smoother but same if not slightly worse economy..

now as stated with the right sensor im continually getting 600+km to a tank of fuel.. loving it