Can the high rpm idle is due to a bad temp sensor (4 Viewers)

[nissanh]

The rpm even after warming up stays around 950. Can the issue be at the temperature sensor? There are two sensors right behind the thermostat area. Which one is the sensor that feeds the ecu to control throttle body? One sensor is skinny and has only 1 wire and the other is wide and has 2 wires. No check engine lights, throttle body is clean, no vacuum leaks, new oem pcv about 10K miles ago. Thanks

 

[Spike555]

Yes it could. But there is a easy way to check before replacing parts, use a live data OBDII scanner to watch the engine temp, that will show you what the ECU is reading.
Just because the gauge reads normal does not mean the ECU reads the correct temp.
I do not know if there are two seperate temp sensors or not, one for the computer and one for the gauge, I do not know.

 

[medtro]

What year is your vehicle? There isn't anything connected to the smaller sensor on mine.

 

[nissanh]

Mine is 2000 and there are two wire plugs, one for the smaller and one for the bigger sensor. Have an extra temp sensor removed from a working cruiser, feel like swapping it in.

 

[medtro]

If you have 2 wire plugs there, try disconnect them one at a time and check your temperate gauge reading. If the temperature gauge works as usual, then the disconnected plug is wired to ECU.

 

[jerryb]

is it in closed loop running that high?

 

[nissanh]

Sorry, not sure what is close loop is. Can you please clarify? I have 950 ish rpm even after 5 hour drive.

 

[white_lx]

Sorry, not sure what is close loop is. Can you please clarify? I have 950 ish rpm even after 5 hour drive.

Closed Loop is when the oxygen sensors control the fuel injection amounts (air flow is not really controllable). When your vehicle is warmed up, it should be in closed loop, unless some sensor values are missing / unusable.

Can you monitor data streams? First double check the system is in closed loop and take a quick look at all sensor values. After that I would zoom in at the fuel trims. Compare bank 1 and bank 2, etc.

If you have a leaky injector, your RPM could go up. Also when you have a vacuum leak. You mentioned there were none. How did you verify this? Could be an intake manifold leak, etc.

 

[Spike555]

It also goes open loop when you are coasting with your foot off the gas.

 

[nissanh]

Thank you for the replies.

 

[jerryb]

it also goes closed at some predetermined % of throttle position. This is not what this guy has problems with.

he said no vac leaks, assume temp input then. from maf or sensor. Or i guess AC sig, but its kind of high for that.

 

[PDPerry]

Few years back Bubbles started running a fast idle. Replaced/cleaned all sorts of things w/o any luck.
Then I noticed he was running a bit under-temp, so I replaced the thermostat.
That fixed it!

 

[nissanh]

It was the temperature sensor (2 pin connector). I replaced it with another toyota sensor came from a 92 corolla and now the rpm dropped to about 700. I tested the one I removed and the one I installed in hot water. Righy around 165 Fahrenheit, the old sensor showed 712 ohms and the corolla sensor showed 500 ohms. See the chart to find the resistance vs. Temp graph.

Thank you!

 

[medtro]

Which one did you change?

 

[nissanh]

^The two wire connector. Part number is 89422-20010. Mine is 2000. It has a 19 mm base. I had this high idle for past 2 years and made a big clunk when going between D and R. Now the engine sounds so good and smooth with only injectors ticking! I had a sensor removed from another 2000 cruiser but it had 8942230030 with tabs on the wire plug connector on opposite side( see black sensor) the green is the one came in my truck.

 

[uzj100]

Where is this located on the engine? Need to replace. Thank you.