2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Thermo Temp Sensor...... Purpose.. and if unplugged what will happen?

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Old 09-24-05 | 11:54 PM
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Thermo Temp Sensor...... Purpose.. and if unplugged what will happen?

The thermo temp sensor behind the waterpump housing, what does it doe.. its purpose, the plug going into it dryrotted and its all messed up.. i have to pull off the intake, go to a junk yard and get a new plug. If I do not have this hooked up How will my engine run? I just put my rebuild in and my rx-7 is running really bad. it will not rev past 3k rpm unless i barely press the gas.. and then if i floor it. it bogs out and stops then stalls out.. it smells like unburned gas.. like heavy rich.
Is this the problem?
If not.. what else could be the contributing factor?
thanks
Old 09-25-05 | 12:06 AM
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Your ECU won’t know wtf is going on! It is the most important link really to tell the computer what types of fuel delivery to shoot at it. Without it the ECU will freak out and start poring fuel into the car.
Old 09-25-05 | 12:08 AM
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okay.. well, its disconnected, my engine light is on and my car is running real rich, would this boggin and hesitation be the key problem to this easy fix
Old 09-25-05 | 12:16 AM
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You are either bogging from the rich mixture, pore grounds, clogged filter system.
Old 09-25-05 | 08:07 AM
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In general topics, under suggestions, there is a thread entitled FAQ, etc, by me. Read it, and get back to us. This is getting old very fast.

PEACE THE DOG
Old 09-25-05 | 11:59 AM
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The water thermo sensor is a very critical part. Without it, the ECU basically goes into "dump as much fuel as possible" mode and the car will run very poorly. I've seen some cars respond differently without it though. On one hand, I've talked to a guy that said that his car still drove alright, it just had a little less power. On the other hand, when mine broke (and I mean physically broke, I still have no idea what happened) the car barely had enough power to get out of my driveway and was sounding and smelling like an old boat motor.

So yeah, that's most likely the cause of your problem. I don't think you have to pull off the intake to get to it though. I had to unbolt the alternator, but that's it. Good luck.

-Darren
Old 09-25-05 | 04:26 PM
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Originally Posted by iceblue
Your ECU won’t know wtf is going on! It is the most important link really to tell the computer what types of fuel delivery to shoot at it. Without it the ECU will freak out and start poring fuel into the car.
If your thermosensor goes bad, your ECU will default to 60 degrees. It wont DUMP fuel, and your car WILL run, albeit a little on the rich side. Ive seen many cars that have ran fine with this sensor disconnected (I found them disconnected because I scanned the codes and it flashed the thermosensor code).

Last edited by Aaron Cake; 09-29-05 at 11:09 AM.
Old 09-25-05 | 06:01 PM
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It defaults to 80 degrees and that is equal to 176 degrees F. I read that somewhere in the 89FSM on page F2-20.

I win!
Old 09-25-05 | 06:25 PM
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Oh, well ****.. If Aaron said it it MUST be true! You know what little man? Aaron is a mod, and he knows alot about rotaries, but he is also human, and makes mistakes from time to time. The fact is, the ECU defaults to a temperature. If HAILERS says its 80 then it must be, because he sleeps with those damn FSMs.

Last edited by Aaron Cake; 09-29-05 at 11:12 AM.
Old 09-25-05 | 06:43 PM
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Mine was broke (the connector anyway) and my car did exactly what Iceblue described. I was given the exact same exsplanation from Jeff @ Rotary Power while my car was there getting fixed. So from my exsperice and others that I respect, Iceblue is 100% correct.
Old 09-25-05 | 06:45 PM
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Thats fine, I have seen the cars run without the sensor connected, so there it is.
Old 09-25-05 | 06:47 PM
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Originally Posted by J-Rat
Thats fine, I have seen the cars run without the sensor connected, so there it is.
Yeah I am not doubting you, these cars can be a funny beast, and what works for one ,might not for another!
Old 09-25-05 | 06:48 PM
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That I completely agree too..
Old 09-25-05 | 10:45 PM
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I meant to put a C after that 80. It's 80 degrees C the same as 176F. Defaults to that in the ECU. It seems to me 176F is pretty close to normal running temps.
Old 09-29-05 | 01:52 AM
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well now i have the new plug and the thermo temp sensor is plugged in.
the car runs a little better.. but it still bogs...
heres what happens...

Start car.. Runs, Revs like a mother fo...
take off in first reve all the way to 8k if i want
can go to 8k in 2nd also... (however i dont go that high)
but then i hit 3rd and it just goes bleh... and thats it.
starts to bog and jump and hesitate at like 3500 rpm...
if i tfloor it .. it just goes BLEH BLEH and doesnt accelerat
and if i just slightly press the gas .. it will SLOWLY SLOWWLY accelerate.
check engine light is on

probabaly should chekc huh?
Old 09-29-05 | 02:37 AM
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Do a search for "3800 RPM Hesitation" and that should help you a lot.
Old 09-29-05 | 11:13 AM
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Thread cleaned of flames. Some posts were edited, some were deleted outright.

To clarify my original statement about the water temp sensor: "Crazy rich" can I guess be interpreted several ways, but "dumping fuel" into the engine I think goes a little overboard.
Old 09-29-05 | 11:25 AM
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hmm, so thats what that little doodad is hanging off behind the water pump. i still havent completely gone throught the car and logged every little hiccup yet like i usually do, nor had a chance to fetch the proper manuals.

guess i have to make that fault a priority now.
Old 09-29-05 | 01:40 PM
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sounds like your secondary injectors arent coming online. check their plugs, and do a search, this has been covered before.
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