Hey guys, my 1980zx N/A has been doing a strange power surge thing. Once a I rev it above 2000 RPM it launches my tac up in spurts about 500 at a time and surges the engine. It feels to me to be electrical. The FSM tells me in troubleshooting it may be the thermotime sensor, so I took some readings on it and they seem to be off. I decided to unplug the sensor to see what would happen, the car ran but not very well, and the surging started happening after 3000 instead. I returned home and turned the car off, and when I came back a little later it wouldn't start and just kept cranking. So I plugged it back in and it came to life but bogged for a minute until smoothing out. I looked online and can only find those sensors for about 70-100 dollars. Does anyone know where I can get one? Or any other suggestions please. I'm not positive it is the sensor causing these problems but it seems to be off. I'm not even quite sure exactly what that sensor does either, so any info on it would be appreciated.
Thanks.

 

The thermotime switch controls the cold start valve... which should not be activating when the engine is at operating temp.

So did you really mean thermotime switch on the thermostat housing, or CHTS (Cylinder Head Temp Sensor) on the right side of the head between spark plug 5 & 6?

From this thread: https://www.zdriver.com/forums/280zx...sensors-36716/

 

The one that I unplugged is the sensor on the thermostat housing. My Dad and I tried to take resistance readings per the FSM but it was hard to get the probes on the plug ends so the numbers on the meter were jumping around. The FSM also suggested taking the switch out and doing tests in different water temps. We'll remove it if we have to, but if you think it might cause the surging, we will find one and pay the big bucks to eliminate the possibility.

By the way, what does the head temp sensor control or activate?

Thanks for all the help!

 

For anyone wondering, it was the thermotime sensor. Apparently I had been losing a good bit of power because of it too. I replaced it with a new one from eBay for 60$ and it immediately eliminated the surging and power delivery issues.