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Discussion Starter #1
Okay, got my fancy new OBD2 code reader that has the ability to monitor all the engines sensors in real-time, AND display them in readable numbers, not just percentages or millivolts.

Anyway, i noticed since i bought this truck that it idles a tick high, and the reader confirmed it, when warm, the truck idles at around 975rpm. The coolant temperature also NEVER goes above 170 degrees. I see from many parts sites that a 170 is the normal number for this engines thermostat. Seems kinda cold, but, whatever.

In terms of gauge position, ive never seen it creep past the 1/3 mark from the cold side.

Could these two be related, or should I just adjust the idle down to 750?
 

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170 is normal. Your thermostat should open at 170 allowing your coolant to circulate and cool the engine. Remember, 212 degrees is where water boils! You don't want steam to blow your radiator apart :)
 

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Discussion Starter #4
...unless your rad cap isnt sealing =)

I just thought 170 odd seeing as the older iron clad nissan engines, L series/Naps-Z seem to like to run hotter, like 195. My 75HP L20B with a 3 row rad in the 510 runs at 180+ all the time.

But, if nissan specs a 170, you cant argue with them!

Will do on the idle, but, what other things could possibly cause it to idle so high?
 

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well, I have had my fair share of these trucks and its about where they run.. usually a bout a 1/4-1/3 of the way up on the gauge and in my opinion 170 is too cold.

You just confirmed a couple of things I have always wondered about.

1) Nissan's usually run higher on smog output than most other trucks. The cooler temps might have something to do with this.

2) The cooler temps might also have something to do with why the truck never gets very good fuel mileage.. granted there are other factors at play here but running colder would increase the amount of fuel the ECM inputs into the engine

3) Im not sure why the above poster worries about 212 degrees as a boiling point.. Thats why we have coolant and a radiator cap that pressurizes the system. In california though I rarely run more than 30% coolant and 70% distilled water.

4) Im not so sure you can adjust the idle.. Usually those things are non adjustable.

My first place to look would be the timing.. Should be 10 degrees BTDC

And I would change the thermostat to a 180 at least.
 

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Discussion Starter #7
Well, as per the FSM i revved it 3 times, idled it, and i adjusted the idle down to about 800, still wanders a bit.

TPS says 0% at idle, no mv reading.
 
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