sam12345

iTrader: (1)

Well the three things you are doing are a waste of money and will do nothing for gas mileage. Go with the specified spark plug in your manual, kn will only get you a "performance sound" and nothing else, royal purple will be ok but I doubt that will help mpg much. Put a new air filter on (stock) if the current one is dirty. Clean throttle body, changed the ect, make sur the wires are all good, use premium gas, check tire pressure, the normal stuff! Put a bottle of techtron injection cleaner in the tank

ls400geek

Anyone have a table or list of resistance values this sensor should have for the various temperatures?

Afterall, it's just a variable resistor based on temperature. I just measured this $10 aftermarket one I got off eBay and it was at around 1700 ohms resistance at room temperature here. I put an ice cube up next to the brass and it was shooting up in resistance pretty fast.

If I had a table of correct resistances for various temperatures, I could verify this aftermarket sensor is working as well as the OEM one. I can just suspend it in a pot of water and measure the temperature of the water with an infrared thermometer and the resistance with a multimeter at the same time.

ls400geek

.. for the ECT sensor I just bought of ebay for $10:



It would be cool if others could post some data like this for their ECT Sensors (both aftermarket and OEM). And perhaps some examples of ones that are 15 years old showing how they are off due to the hardened wax inside.

I guess I'll be replacing my OEM one (original 15 year old one I presume) with this aftermarket one and measuring the old one with the same method I used to measure this aftermarket one: Stand the ECT sensor on end in a copper or aluminum clad pan with water in it over the stove. Measure at various temperatures using my infrared thermometer and measuring with a digital multimeter. [I suppose these could be done with the sensor in the car engine as well for existing installations.]

ls400geek

Thanks to some help I found a chart of acceptable ranges for the OEM TX40 ECT Sensor:



It appears that my $10 eBay ECT Sensor falls into the acceptable range.

I'm going to pull out my 15 year old OEM ECT Sensor tomorrow and measure it in a pan of water with infrared thermometer and ohm meter, like I did with this aftermarket one. I'll post the results. I am hoping it will show that it is off (being of higher resistance).

Yamae

ls400geek, did you check other items? Of course the resistance is a very important item but that is only a part of issues for an ECT sensor. The Galvanic series is another important issue, you know. I knew some of my friends who failed using cheap aftermarket sensors having the Galvanic corrosion at terminals.

ls400geek

The aftermarket ECT sensor I have appears to be made out of brass (with a copper crush washer). I am not sure its exact metal alloy makeup but for now it's working properly (using tap water in a pot). I suppose I'd have to check it after I put it in the car after a few days, then a few months, then perhaps after a year, to see how it's holding up.

You make a good point though and am thinking OEM would be definitely the best way to go

I want to see if my old sensor is bad though (it's 15 years old).. I am curious how it will measure up. I hoping it'll be off because I am only getting 15.5 mpg at the moment in the city. I've already replaced the two air filters, 2 timing pulleys, 1 drivebelt pulley, replaced the bad transmission mount, did a 4 wheel alignment, fresh oil, fresh transmission fluid and a BG 44K fuel treatment--still only 15 1/2 mpg in the city, *sigh*. I ordered 10 new electrolytic caps (low ESR) based on your post here (thanks)--maybe that'll help the gas mileage; I bet they are all rounded and bulged out (the electrolytic caps) on the ECU. Only other thing I can think of is to clean the throttle body. (The spark plugs were replaced 60,000 miles ago in 2007).

(I have a 1998 LS400.)

Yamae

Hi ls400geek, I find you are a person who is quite familiar to things. I am sure you can improve the gas mileage soon.

When you have posted the temperature and the resistance curve for the first time in this thread, I quickly thought that there came a guy who can expect. No one has ever been posting the actual values in the past here. I also thought that it would be better to pay attentions to other important items such as the Galvanic series and the material of the plastic. But since you know things very well and I think I'd better to keep my mouth shut.

Regarding the gas mileage, the only thing I'd better to inform you from my actual experience on a 98 Celsior 150,000km is that the gas mileage was improved nearly 10% after I cleaned the MAF sensor using a MAF sensor cleaner.

ls400geek

Actually, I'm a woman that is a total newbie to LS400's (with a little knowledge of mechanics & electronics--but specialize in computer programming) and I have a great deal of respect for you. I wish I had not bought this aftermarket ECT sensor after you mentioned galvanic corrosion--it's something that would of never crossed my mind. I don't know things that well at all and I so very much appreciate all your help--I'll be recapping my ECU thanks to your information (already ordered the 10 caps from digi-key.com.) Please don't keep your mouth shut!--oh my then I wouldn't learn much at all lol.

I can't wait to recap ECU, play with MAF, clean TB and change out this ECT sensor and see how everything runs. Thanks

PureDrifter

iTrader: (10)

'98-00 aren't known for having many ECU issues, in fact in the past 9 years I can only recall 1-2 members ever posting about issues with them.

If the caps aren't leaking I would leave it alone.

omarg

just bought 89422-20010 for the GF's 2000 LS400. Found out that 98-00 LS use 89422-30030. Parts cost the same. Anybody know if they differ? Hope it works. Bought it on ebay new for $37 shipped.

Legender

New for that price is pretty good... what brand is it...

Just tried to buy this part from Toyota in Plano and they wanted full list price of $79.70 and... they'd have to order it... Discount price from Sewell is only $48.62...
Thought I could get it cheaper at Toyota... but no.. not that Toyota stealership... ouch... so, just ordered the real thing from Sewell...

8942230030
SENSOR, WATER TEMPERATURE (FOR EFI - ELECTRONIC FUEL INJECTION)

3803

I'd like to share my impressive results after replacing the ECT sensor.

US MPG went up from 15 to 21mpg.

Finn

Am I correct in reading the diagram ie. for the 1991 this ECT is part number 89422-20010?



Apart from OEM sensor which brand would you suggest?

It looks like the same sensor is used in vast number of different Toyotas such as Corolla.

fracmann1

great post i will be trying this

Greg5OH

how often do these things last for? mine is about 5 years old.
Guess I will pull it out and test it, see if it falls into acceptable range.