ZX 1.4i Temperature Sensor?

nesssalmon · Unread post by **nesssalmon** » 27 Mar 2006, 11:33

I am still having problems with my idle speed, cutting out, jumping etc with my ZX. After slowing replacing many parts - Stepper Motor, Coil, Ht Leads,
and checking for vacuum leaks. I am still no further.

But I feel i have narrowed it down to the Temperature sensor (ECU),or the ECU itself.

I have taken the green Coolant temp sensor (ECU) off and run the car, and no engine warning light is coming on? is this odd?

Is this an easy job (just unscrew and replace?)

Also my green plug is on the thermostat housing and my blue sender (temp guage) is further away from the front of the car, are these in the correct position?

zx 1.4i monopoint 1994 Boche MA 3.0

Many Thanks
Robert

AndersDK · Unread post by **AndersDK** » 27 Mar 2006, 22:16

The coolant temp sensor (CTS) for the ECU is located at end of the cylinder head. Earlier types are blue later types are green on the 2pole plastic contact piece.

The sensor is a generic NTC resistor (a resistor element is not polarised). The resistance of the sensor goes towards high when cold - and narrows a shortcircuit when hot.
If & when they fail they usually go open circuit - and they usually show as the hot engine running lumpy & rich idle and sometimes sets the fault lamp - because of the rich running.

Easy to test : With running hot engine : remove plug from sensor then the engine should start run lumpy and rich (open circuit simulates deep frozen engine)
Now shortcircuit the 2 pins in the plug (on the cable) and the hot engine should revert to normal idle (shortcircuit simulates hot engine).

Its important that the engine is hot during this test.
You may interprete the sensor function as a choker - and a failing (open circuit) sensor as a sticking choker.

Otherwise an irritating error on lumpy engine running which seems not to be cured by any remedy - may be any MAP or airflow sensor defective or gunked by oil from intake - typical behaviour.

nesssalmon · Unread post by **nesssalmon** » 27 Mar 2006, 23:01

Many thanks for your help. I have been driving today with the green plug off the sensor, and i have not really noticed much difference. Perhaps the idle speed was a little higher and pulsing (I thought the ECU was supposed to revert to some emergency setting)

So maybe the sensor is stuck open (Cold Engine)? I will do the test tommorw and see how she runs.

The only thing that is confusing is which colour is my coolant temp sensor as you say it could be either Blue or Green?

Another possibility is the stange black canister fittd to the right hand side front inner wing with vacuum hoses going in and out? not exactly sure what this is as my model is not supposed to have an MAP sensor.

Cheers
Robert

lighteninguk · Unread post by **lighteninguk** » 28 Mar 2006, 13:16

the black canister is the charcol canister and is part of Evaporative Emissions Control. this is mainly used when the engine is hot as it burns off unwanted gasses. (i think) you can usualy feel the purge valve pulsing/clicking when the engine has warmed up.