Fc electric/computer problem?
 

Ok! Here goes bear with me people :)


Model:
*FC3S TurboII 1991
*German build
*PowerFc
*Koyo Rad
*Other mods that i concider unsignificant too the problem.

The Problem: After i have driven the car for about a minute or two and the engine ist starting too get some temperature the water temperature on my POWERFC suddenly start jumping up and down ranging all the way from -5 Celsius and up too the normal 80-90 Celcius operating temperature.

Symptoms: Car coughs and jumps and eventually drowns/dies at any pedal pressure/throttle pressure

What i THINK causes the problems:

When my car starts jumping on the watertemperature my Injector Duty also jumps up too compensate for a cold engine, im usualle at 27-34% Inj. Duty when full throttle but when i look at my Commander my PFC is actually at Inj. Duty 55- 70% when the water temp drops.


What people tell me to do: Change water temp sensor ( tho this is unlikely too be broken). Also they want me too draw a new signal cable from the sensor and onto the PFC. They want me too use a multimeter too find out which wire is the water temp connection into the PFC and somehow do a new one.

SO! My question too all you gurus:

*Where do i read from with the multimeter?
*What should the meter read haha?
*Ill just solder it on when i find it?

Thank you for your time guys :)

Thomas

No need to run a new wire unless you first verify that the existing one is not working. No need to replace the sensor unless you can verify that it is not working, unless you want to invest in a new one on a guess.

Get a wiring diagram. Find the pin on the connector at the ECU. Check the voltage on that pin and compare with that listed in the online factory service manual. If the voltage is correct, it is not the sensor or the wire. If the voltage is not there, disconnect the connector at the ECU and at the sensor, and check the riesistance between the two ends of the circuit using the ohms function on your multi meter. If the resistance is zero, there is continuity. Then check the resistance from either end to a good ground; it should be infinity. If it is low, the circuit is shorted.

If the circuit is ok (low/no resistance, and infinite resistance to ground), the circuit is good and the improper voltage is probably due to a bad sensor. Then you should replace it.

Does your ECU report no trouble codes?

Thanks for you answer. No im having no error code readings and the idiotpanel shows nothing either.

As im using a PFC, it wont be reset or anything if i disconnect it will it? Its gonna operate as normal if i disconnect the PFC connector and then plug it back in after measuring the pin in question?

You want to measure the voltage on the water thermo sensors input wire, at the computer, with all plugs connected up. You backprobe the wire in question.

Pulling the plug off and measuring the output of the water thermo sensor is unproductive. Ain't no voltage there to be measured.

Maybe pulling the plug off the computer and reading the resistance would be productive, not voltage.