CHT Sensor Question

[Targa Me]

Hello Everyone,

Does the CHT sensor relay data to the ECU for emission purposes?

Thanks in advance.
Larry

[steely]

Primarily, I think the O2 sensor is what is used for emission purposes, but the CHT does play a role.
Its info is fed to the DME and, among other sensor info, it's used timing / ignition mapping and idle control. There is some info under Engine Management in Bentley's shop manual.

[scarceller]

I assume you are talking about the 3.2L?

The CHT sensor is a critical component to calculating fuel for the given amount of air measured by the AFM. So in a sense it certainly is emissions related because if it's out of spec and say it reads lower temp than the engine really is it will result in rich mixtures that will fail emissions. For example if you unplug the sensor on a fully warm engine it tricks the DME into thinking the Engine temp is stone cold and the fuel increases dramatically and the engine starts to idle hunt and usually results in stalling.

Bottom line is that the CHT sensor must be within spec for fueling the motor properly.

[Targa Me]

Thanks Dan.
That reminds me, I think I have a Bosch Motronics manual stashed somewheres.

[steely]

You're welcome - Sal knows much more than I do on the subject, and the Motronics book is of course a better ref than the Bentley.

[darrin]

fwiw, the older CHTs were of a single wire variety that all seem to fail after a while, the newer (replacement) version uses two wires and appears to be more reliable (my '86 had a single wire that failed in the mid '90s -- the replacement 2 wire is still running fine)