Does The Ecu Temp Sensor Affect Fuel Consumption ?

[Munkyb0y]

My mechanic told me that 2 common things that cause bad fuel economy on skylines are the 02sensor, and the ecu temp sensor.

changed my 02 sensor a while ago, no improvement.

so is the temp sensor worth trying?

i think they're only about $50.

[RB30-POWER]

It sure can, if it is telling the ecu the engine is cold, it will always be using enrichment that isn't needed.

But all these sensors are easily tested for correct operation.

You don't just go changing things unless you like wasting money.

[Munkyb0y]

well seeing as i dont like wasting money

please explain. tested how?

[WazR32GTSt]

$50 from where?

nissan?

[RB30-POWER]

Two ways you can check it.

Firstly by disconnecting the plug and using a multimeter measure the resistance across the two terminals at the different water temps.

Spec is

20deg 2.5k ohm

80deg 0.3k ohm

Second way is to measure the voltage between ecu pin 28 and earth at the different water temps.

Spec is

20deg 3V

80deg 1V

As long as the test results are somewhere close to the spec it isn't faulty.

Hope that helps.

[paulr33]

ive never seen a water temp sensor cause bad economy

if u want to test it, unplug it and drive around for a week

the car will be fairly upset. mind wouldnt even start with a shagged water temp sensor. so id be suprised if yours would work, but get crap economy.

[RB SANDY]

How maney k's are you doing with 10l or a full tank and what 98 fuel are you useing, try shell optimax I put bp in car and the economy was bad

so try shell

Edited September 29, 2006 by RB SANDY

[Cubes]

I know mines a prehistoric R32 but mine would start and run ok with the water temp sensor disconnected.

I ran in to fuel economy problems a while back. All of a sudden dropped from mid to high 400's to 350km's per tank almost overnight.

Replaced o2 sensor with new item, had already replaced water temp sensors and they were reading fine on the pfc h/c. I replaced injectors and bang.. fuel economy was back.

Driving style also has a little to do with economy. With mine at least it makes a considerable difference. If I change up a shade over 2000rpm I get pretty damn close to 500km's per tank. If I stretch out the gears a little to 3000rpm with light throttle fuel economy hangs around the low 400's.

The odd boot here or there doesn't appear to make a noticable difference but if always up on boost and booting it it does and I only just scrap in at 400km's per tank (~50-52litres).

The RB20DET however, didn't seem to matter how I drove it, always returned 450-470km's per tank.

I feel like a broken record. I've said that so so many times.

[Munkyb0y]

Two ways you can check it.

Firstly by disconnecting the plug and using a multimeter measure the resistance across the two terminals at the different water temps.

Spec is

20deg 2.5k ohm

80deg 0.3k ohm

Second way is to measure the voltage between ecu pin 28 and earth at the different water temps.

Spec is

20deg 3V

80deg 1V

As long as the test results are somewhere close to the spec it isn't faulty.

Hope that helps.

that helps alot. thanks man. will check that out.

[xRHETTx]

How maney k's are you doing with 10l or a full tank and what 98 fuel are you useing, try shell optimax I put bp in car and the economy was bad

so try shell

10.9L/100kms using Boost98. Works good, hella cheap too. Stockish R32 gtst.

[Munkyb0y]

How maney k's are you doing with 10l or a full tank and what 98 fuel are you useing, try shell optimax I put bp in car and the economy was bad

so try shell

i'm getting about 15L/100kms. BP Ultimate 98.

Ive tried mobil, caltex, but not shell. keep hearing so many bad things about optimax.

At the end of the day, highway vs city/short trips, makes a huge difference.

that's why u get some R33 owners claiming 500kms to a tank, and others getting 250kms.

Will be hunting down a cheap used safc2 (anyone selling???) to fit and tune soon, but i want to make sure the temp sensor is doing its job first.

[GreddyGo]

The Temp sensor is one of the vital reading's the ecu requires for fuel consuption!

Do the check as described above with a multimeter!

If it's out of spec replace it.

Cheers

Josh

[RB SANDY]

what is bad about shell, i have tried the 100 octane and the car goes better.

[GreddyGo]

I'm not sure, I haven't used it purely because of the rumours.

I was told it goes off quickly compared to the others.

Still rumours though.

Cheers

Josh

[Munkyb0y]

do i keep the car running when measuring the resistance across the temp sensor terminals?

or motor off, ignition on?

or other ??

also, just to verify, this is the sensor i'm checking, right ?

[Cubes]

I do all local driving. ZERO highway.

Driven correctly the 3ltr returns the same fuel consumption as the rb20det.

R33's for what ever reason tend to have considerably worse fuel economy compared to the little old r32's. Maybe its the greater weight, maybe its the vct or something who knows.

[RB30-POWER]

do i keep the car running when measuring the resistance across the temp sensor terminals?

or motor off, ignition on?

or other ??

also, just to verify, this is the sensor i'm checking, right ?

disconnect the plug and measure the resistance on the engine when its cold (first thing in morning), water temp will be around 20degC then.

then again after driving the car and its up to normal operating temp disconnect it and measure the resistance. operating temp is around 80-90degC.

all test with engine off.

If you prefer to measure voltage you will need igntion on and the connector plugged on.

[Munkyb0y]

I tested the resistance at the temp sensor terminals.

2.85k ohms when cold/sitting overnight.

0.31k ohms when warmed up/after 15min drive.

so it looks good to me.

cheers man. thanks for your help.

if anyone is selling a used safc2, cheap, PM me.

[otto]

if you do alot of short drives as opose to afew long drives fuel economy will suffer big time, just recently i moved closer to work so im only a 10min drive away so if all i do is drive to work my car is always running the richer(cold engine) maps as it doesnt get much time to warm up and my fuel economy has dropped from 450 odd km to 350 odd km's

[Cubes]

Which is why its especially important to run a genuine thermostat as they get the car up to operating temp and out of the water temp correct table within 1-2km's.

Otto, if you run a pfc you can lean the water temp correct table out to all buggery until the drivability begins to suffer. I was able to take out a considerable amount of correction. I've seen a few maps from different tuners now and find it interesting they almost never touch the water temp correction table.