The temp gauge on my 86 gxl has stopped working. I have also been getting really bad gas milage/ hot start problems. It seems to me that its the water temp sensor. My thoughts are:

-sensor fails, so gauge doesnt read
-no reading from sensor so car dumps fuel
-car dumps fuel so engine floods

does this sound right? If it does, I need to know how many/where the various coolant sensors are so I can replace them or test them.

Also, any similar experiences you guys have had. -thanks -Matt

 

the temperature sensor for the temperature gauge and the one for the ECU are two different ones. The odds of both of them failing at the same time is probably pretty slim. I'm not sure what could cause the car to start running badly though.
Patrick

 

Is the sender plugged in? It's on the passenger side of the engine, all the way back, under the oil sender. It looks like a bolt with a spade connector sticking out.

 

jprx7 is right, the two problems will not be directly related. The wire has probably fallen off the gauge sender (see pic). Poor mileage and hot-start problems together sounds like low compression...

 

Oops, forgot the pic...

 

its not low compression, i did a compression test, 104,104,104 on the front rotor 95,95,95 on the rear.

I'll check the wire tomorrow, and see if the one next the the oil pressure sender is plugged in. (thats the one for the gauge right?)


Oh, and if there are two seperate sensors (cpu/gauge) where are the BOTH located?

 

Where did you get this picture?

 

Any info on HOW MANY temp sensors there are?
and where theyre located?

thanks

 

bump?

 

bump?
how many sensors? and where, maybe?

 

Correct.

The gauge sender is shown in the pic; the ECU thermosensor is screwed into the back of the water pump housing (look under the alternator).

FD FSM.

ECU coolant thermosensor on the back of the water pump
Temp gauge sender in the engine's rear plate under oil filter
Intake air thermosensor in the TB inlet (Turbo) or intake plenum (NA)
Intake air thermosensor in the AFM
Electric fan temp switch (if fitted) on top of thermostat housing (S4) or back of water pump (S5)
Radiator temp switch in the radiator bottom tank
Sub-zero start temp switch in the oil pan
Exhaust temp switch above catalytic convertor

 

NZconvertible, you are a good person.

 

Thank you.

 

Which of the above would most affect gas mileage, cause my fuel consumption is CRAZY!

 

The ECU thermosensor would be the only one I'd consider. You can test it as per the FSM's instructions.

 

second that, especially since you are experiencing hot start problems.. And you are right about the fuel dumping... its a safety measure to try and get the engine cooled down and prevent detonation...

Interesting, cause my haltech has it as well, the damn connector fell off one day while i was driving and i thought the car had blown up... I still have the scar on my hand from putting it back on and melting my flesh to the water neck!!!

 

Use this, read all of the little bastards out, lol...

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/

 

I've always wanted to do ecu pin checks,
but i'm nearly usless when it comes to electrical stuff, it may be time for me to learn.

Nice info by the way, once in have the major "physical" problems tackled, I'll go on to the brain!!!!