M20 Temp Sensors

[E34-520iSE]

Hi guys!
Got a bit of a technical question here. What is the deal with the M20's temperature sensors? There are two present, but I am not 100% sure of which one does what, what their hot and cold resistance is and which loom plug connects where. I have a cold start issue that I'd like to get to the bottom of!

Cheers,

Shaun

[Jon K]

Hi guys!
Got a bit of a technical question here. What is the deal with the M20's temperature sensors? There are two present, but I am not 100% sure of which one does what, what their hot and cold resistance is and which loom plug connects where. I have a cold start issue that I'd like to get to the bottom of!

Cheers,

Shaun

There are more than 2 temp sensors. If you mean coolant temp - one is for the gauge on your cluster... the other is for the ECU to bring the car out of cold-startup.

[E34-520iSE]

There are more than 2 temp sensors. If you mean coolant temp - one is for the gauge on your cluster... the other is for the ECU to bring the car out of cold-startup.
Hi Jon, thanks for that. Is there any other info you can pass on regarding M20 coolant temp sensors? Also, the other temp sensors you know of.

Cheers,

Shaun

[Jon K]

Hi Jon, thanks for that. Is there any other info you can pass on regarding M20 coolant temp sensors? Also, the other temp sensors you know of.

Cheers,

Shaun

If one of the coolant sensors is blue, I believe that to be the one that is going to the ECU but please do not quote me on that. The only other temperature sensor I can think of on your car would be the IAT (intake air temperature). That will be close to the throttle body somewhere. If that is out of whack, and say it feeds the ECU a "really hot" (false) reading, the ECU may make an attempt to retard the timing to prevent (non-occuring) detonation. I am not sure if the ECU can pull the timing so far that it won't start, but hey, germans are weird people.

[Jon K]

additionally:

have you considered your idle air control valve? Does the car idle odd? Vacuum leaks can also arise when the motor is cold and close off when things expand while the motor is warm. Something to consider.

[E34-520iSE]

Hi Jon,
No problems with the idle - I am lucky enough to have a quiet & smooth idle, with no valvegear noise etc. My problem has only shown itself now that temperaturess are hitting -2 at night, when I finish work. If the outside temp is mild it starts perfectly. Strange huh? Still looking for any help with temp sensor cold/hot resistances.

Thanks again Jon!

Shaun