Coolant Temp Sensor = better MPG?

[silverkouki]

Hello all,

I had a chat with a buddy with an Altima the other day and he was explaining to me that he was getting increasingly bad MPG in his car every week.
He's tried almost everything: O2 sensors, spark plugs and wires, distributor cap and rotor, fuel filter, air filter, fuel system cleaner, wheel alignment, tire pressure, etc etc etc..... nothing's worked.

Then he told me about the Coolant temp sensor, how it can go bad (and not throw a check engine light) and when it does go bad, it'll tell the ECU that the engine is running hot when it really isn't, which then causes the ECU to richen up the A/F to cool the engine down.

He replaced it (for under $20) - and within a few days, he said his MPG was going from low 20's before the replacement, to mid 20's sometimes higher 20's (highway).

My question is: Can replacing the coolant temp sensor really improve Gas Mileage?
If we replace the CTS in our 240's will our MPG get any better?

(btw, I've searched, didn't find any conclusive results)

:confused:

[attracted]

if your coolant temp is bad..you will definitly run richer...sometimes when ur car is hot and you turn it off and try to start it again it wont start since the ecu will think that engine is cold and try to dump cold start fuel in there so it will flood the cylinders

[Giebs]

replacing the ECT would only help unless it actually is bad. but usually when they go bad, they turn on a check engine light like you said.

[projectRDM]

Correct, a bad CTS will signal the ECU into thinking it's running the cold fuel map, but it will not throw a code like mentioned above. Test the resistance on the sensor and replace as needed.

[Giebs]

...but it will not throw a code like mentioned above.

lol, guess i got that answer wrong on my test last week :-/

[0wn3r]

lol, guess i got that answer wrong on my test last week :-/

I believe it threw a code on my S14 SR...

[dirtdiggler666]

i have a s14 ka my temp needle started bouncing up and down then after my cel came on. my sensor has a bad connection will this change with my cel on??

[silverkouki]

thanks guys.

Ill test the resistance on the sensor and see what the outcome is.

People should remember that the correct sensor has two wires and is called the Engine Coolant Temperature (ECT) sensor which feeds the ECU. The other sensor has one wire and is the coolant temperature sender for the temperature gauge ONLY.

But I think everyone should replace it anyway (if they haven't recently) even for the hell of it because it costs only $18 and it takes about 5 minutes to replace...

[blueshark123]

I actually had the same problem on my maxima but it did throw a cel and after replacing it the gas mileage improved.

[Giebs]

so just looked through my fsm for '89 240, and trouble code (check engine light) #13 was engine coolant temperature sensor.

[attracted]

just so you guys knwo theres two ect sensors on an sr or a ka

on which is a 2 wire which goes to the ecu and the other one is a one wire which only goes to the cluster...
so it could be that your cluster shows the good temp but the ecu is not reading it or vice versa

[nissanguy13]

just so you guys knwo theres two ect sensors on an sr or a ka

on which is a 2 wire which goes to the ecu and the other one is a one wire which only goes to the cluster...
so it could be that your cluster shows the good temp but the ecu is not reading it or vice versa

yes sir.

Correct, a bad CTS will signal the ECU into thinking it's running the cold fuel map, but it will not throw a code like mentioned above. Test the resistance on the sensor and replace as needed.

Took the words right out of my mouth

[240boy90]

Yes it does man. Saves you gas, but mine was bad. I use to have the same problem. When I drove on a steady speed it would bog like a subie (it wasnt my maf). I use to put $15 bucks in my tank every sunday night for a week of work and by the end of the week I would be all dried out. Ever since I change the temp sensor I noticed that I had a lil' more gas in my tank that i use too (about a little less than half of a quarter more that before). Kind of a primative way to test it w/o the actual MPG but the proof is in the pudding.

[projectRDM]

i have a s14 ka my temp needle started bouncing up and down then after my cel came on. my sensor has a bad connection will this change with my cel on??

The gauge sender has nothing to do with engine control, so the CEL can't be related to that.

[silverkouki]

I think that the coolant temp sensor is often overlooked.

No one would know to change this sensor out. Even with the Haynes manual and their troubleshooting list for fuel economy, there's no mention of the coolant temp sensor.
The only hint the Haynes manual gives is if you actually read the part on the replacement of the coolant temp sensor. There's a small blurb telling you to handle the sensor with care cause damaging it could lead to a host of problems including fuel economy.

[98s14inaz]

I'm going to look into this. I bet the sensor on mine needs replacing too. I searched around on google and nearly every nissan forum has a thread like this saying to replace the temp sensor. Thanks.

[s13for_me]

im still getting bad gas mileage. i replaced everything even the CTS and the CTS sending unit and still getting low MPG on my s13. My temp gauge is sitting at the 3rd line from the bottom when engine is in normal operating temp. but my friends gauge is in the middle. what could it be?

[98s14inaz]

im still getting bad gas mileage. i replaced everything even the CTS and the CTS sending unit and still getting low MPG on my s13. My temp gauge is sitting at the 3rd line from the bottom when engine is in normal operating temp. but my friends gauge is in the middle. what could it be?What shape is your motor in? If you have bad compression or other issues the car will run but may suffer in fuel economy. There is so much that can affect the gas millage.

[garagelu]

im still getting bad gas mileage. i replaced everything even the CTS and the CTS sending unit and still getting low MPG on my s13. My temp gauge is sitting at the 3rd line from the bottom when engine is in normal operating temp. but my friends gauge is in the middle. what could it be?

Thermostat could be acting up. If your car is running too cool due to the thermostat staying open, the ecu will think the engine is still cold and dump more fuel in. This results in less mpg.

[jskateborders]

I use to put $15 bucks in my tank every sunday night for a week of work and by the end of the week I would be all dried out.
what. Wtf do you drive, and where too? I fuggin use like 80-90 a week