Temperature gauge Question...

[rsmithdrift]

So I was trying to figure out what was wrong with my car and I wanted to test the Coolant Temp Sensor. To check it I followed these directions:

to test your cts get an ohm meter and unplug the sensor and check the resitance of the sensor. you will also need a thermometer to check the temp of your coolant. the values are as follows:Resistance 2.1 - 2.9 K ohms at 68 deg F 0.68 - 1.00 K ohms at 122 deg F 0.236 - 0.260 K ohms at 194 deg F

I got a reading of 1.9 after starting the car and pulling it into the garage. (Temp gauge still low as it'd go)I got a reading of .35 once the car was fully warmed up (temp gauge directly in between C and H)

But the thing is, I have no clue what that means. I'm sure it warmed up a little bit pulling into the garage and was prolly at like 90 degree's or something, but when I tested it hot, I have NO CLUE how hot it actually is...

So that's my question. How hot is the water when the gauge is at it's various locations? IE. How hot is it when it's at normal operating temperature in the middle, and how hot is it when it's at H?

[1KleenS13]

What scale did you set your meter to? I think your sensor is ok. If you do the conversions from ohms to k-ohms or vise versa I think your sensor is within spec. Another idea is to take the sensor out of the car and put it into a cup of water with a thermometer, and ohm the sensor out to figure out what temp corrulates to what ohm.

[rsmithdrift]

lol. I actually did EXACTLY what you said....

I had a spare (the origional) CTS in my tool bag, so I got a pot of water boiling (212*f) and it read .25ohms. which is spot on...

So I cleaned up the connector and put it in my car and tested the new one from autozone that was in my car and it read .30ohms at boiling... But it made no difference the car still runs EXACTLY the same. So apparently it was close enough. IDK what's up with my car.... maybe my 02 sensor went bad when it was running pig rich all last year...

How do you test the 02 sensor?? I did what the manual says and checked it with the car in diagnostic mode and it blinked like 10 times in the 10 seconds instead of 5... but is says it should blink ATLEAST 5 times in 10 seconds, so I think it's ok if it blinks more... but it was blinking like CRAZY. It was like 10-15 times in 10 seconds.

[1KleenS13]

To test the o2 sensor the best way to do it is with a graphing meter, so you can see how fast it is reacting (crosscounts). But with a standard meter tap into the wire with a "T" pin and read the voltage. 0-1volt scale. If its rich its gonna read about 800mv+, if its lean it will read lower 500mv- or around 500mv. The meter will eratically read rich and lean conditions because the ecu is trying to maintain 14.7 a/f. You could also have a lazy o2 sensor, that wont read a rich or lean condition, the crosscounts will be there but they will favor on way or another. Go to the link and you will see exactly what I am talking about. http://www.aa1car.com/library/o2chart.gif

[vancouverbc]

you test o2 sensor by unplugging it and seeing how the car runs.

zerothread/296414

[rsmithdrift]

you test o2 sensor by unplugging it and seeing how the car runs.

zerothread/296414

Well, I just went and did what you said...

I unplugged the 02 sensor and drove around and though it felt maybe a little softer, it drove EXACTLY the same....

When tested with the voltometer I got a steady 500-650mv (set to 200mv) or 0.05-0.06v (set to 20v) The reading slowly moved up and down between those limits.

According to what you said that's lean... Hell that's REAL lean.

Didn't you say it should be at 0.2-0.8 on the 20v scale??

[vancouverbc]

Well, I just went and did what you said...

I unplugged the 02 sensor and drove around and though it felt maybe a little softer, it drove EXACTLY the same....

When tested with the voltometer I got a steady 500-650mv (set to 200mv) or 0.05-0.06v (set to 20v) The reading slowly moved up and down between those limits.

According to what you said that's lean... Hell that's REAL lean.

Didn't you say it should be at 0.2-0.8 on the 20v scale??

what problem are you diagnosing? if your problem didnt go away with the o2 sensor unplugged , the o2 sensor prolly isnt the problem. the o2 sensor has to be completely warmed up before it will give accurate readings. its better to just have a second o2 sensor around to test. you really need to know what you are doing to use volt meter to test it.

[rsmithdrift]

what problem are you diagnosing? if your problem didnt go away with the o2 sensor unplugged , the o2 sensor prolly isnt the problem. the o2 sensor has to be completely warmed up before it will give accurate readings. its better to just have a second o2 sensor around to test. you really need to know what you are doing to use volt meter to test it.

I'm trying to fix whatever is causing my car to run lean, hesitate, stumble, and loose power below 4,000 rpm. Also the idle drops dangerously close to stall when you first put in the clutch, and then it idle's too high once it recovers.

And yes the car was FULLY wamed up the whole time and the exhaust is extremely hot, like hotter than normal. My MAF runs 1.09v at idle, my cts runs 0.30-0.35ohms fully warmed up, the tps reads correct ohms and voltage, the knock sensor won't read any ohms however.... very odd considering the car runs significanly worse with it unplugged. I checked thouroughly for vacumn leaks and couldn't find any. AIV is removed, and BPT valve is removed. EGR valve is still attached but not hooked up, vacumn lines are disconected/blocked so it shouldn't be doing anything.

[vancouverbc]

if you sit around

I'm trying to fix whatever is causing my car to run lean, hesitate, stumble, and loose power below 4,000 rpm. Also the idle drops dangerously close to stall when you first put in the clutch, and then it idle's too high once it recovers.

And yes the car was FULLY wamed up the whole time and the exhaust is extremely hot, like hotter than normal. My MAF runs 1.09v at idle, my cts runs 0.30-0.35ohms fully warmed up, the tps reads correct ohms and voltage, the knock sensor won't read any ohms however.... very odd considering the car runs significanly worse with it unplugged. I checked thouroughly for vacumn leaks and couldn't find any. AIV is removed, and BPT valve is removed. EGR valve is still attached but not hooked up, vacumn lines are disconected/blocked so it shouldn't be doing anything.

if you idle very long, your o2 sensor will read lean. you have to take it out for a spin to heat it up good. none of these tests will get you very far. you pretty much have to substitute known good parts ie maf, ecu, etcYou can buy the parts cheap in the classified forum.

[rsmithdrift]

if you sit around

if you idle very long, your o2 sensor will read lean. you have to take it out for a spin to heat it up good. none of these tests will get you very far. you pretty much have to substitute known good parts ie maf, ecu, etcYou can buy the parts cheap in the classified forum.

I had just run full throttle down the street, pulled into the garage, left it idling, went in and got the voltometer, and put it on... Though at first it was reading 1600mv(set to 200mv) or 0.16v (set to 20v) and it dropped down steadily and stabilized at that value that I posted earlier.

Could that knock sensor that's not reading any ohms be causing this??

[1KleenS13]

Your ECU is probably not the problem. This is how your ECU works Input(various sensors)...........Logic (ecu)...............Output(how the car runs). Look for the obvious stuff first Vac leaks, get MAF cleaner and clean your MAF, IAC, etc. KISS method (keep it simple stupid). The knock sensor is a piezoelectric sensor (produces it own voltage), much like the O2 sensor, To test The knock sensor LIGHTLY tap on the block while looking at a scan tool and read the knock.

[vancouverbc]

I had just run full throttle down the street, pulled into the garage, left it idling, went in and got the voltometer, and put it on... Though at first it was reading 1600mv(set to 200mv) or 0.16v (set to 20v) and it dropped down steadily and stabilized at that value that I posted earlier.

Could that knock sensor that's not reading any ohms be causing this??

Ok, your O2 sensor is probably correctly reading a lean condition.(at idle) your spark plugs should be white if you are lean. you have checked for vacuum leaks and changed fuel filter.

do you have a knock sensor trouble code. the fsm says you have to have an ohm scale above 10 million ohms to read.

http://www.obd-codes.com/p0325

search subject title for lean and see what suggestions come up.

Modified by vancouverbc at 1:08 AM 2/2/2009

Modified by vancouverbc at 1:23 AM 2/2/2009
Modified by vancouverbc at 3:50 PM 2/2/2009

[rsmithdrift]

One milliohms?? I don't think my ohmeter goes that high. It goes to 2,000kohms, is that high enough???

Anyways, It's not the ecu, I've swapped the ecu's with no effect.

And no, my ecu thows NO CODES... it shows code 14 only which is the speed sensor circuit which I cut to disable the governor and has no effect on the car...

[vancouverbc]

One milliohms?? I don't think my ohmeter goes that high. It goes to 2,000kohms, is that high enough???

Anyways, It's not the ecu, I've swapped the ecu's with no effect.

And no, my ecu thows NO CODES... it shows code 14 only which is the speed sensor circuit which I cut to disable the governor and has no effect on the car...

Sorry, that was a mistype. it should be 10 million which means your meter wont work.

BTW, a normal 240sx is very rich at idle ie almost 1 volt.