5 replies to this topic

[Ian Hardaker]

I have a 1994 Cooper SPI, and the Lambda heater relay doesn't seem to come on. I know it is supposed to come on when the Mems grounds the Black and Green wire from the relay, but it never seems to happen. I have put a separate ground on this wire and it is now on all the time that the engine is running... When is this supposed to happen? Do I have a duff Engine Management unit?

[Steve220]

Usually comes on at first ignition in order to get a reading from cold start.

[Ian Hardaker]

So it should be on all the time?

[viz139]

A lambda sensor is meant to be mounted as close to the engine as possible so it gets its heat from the hot exhaust gases. This is not possible with a cold engine so a heater is fitted to the sensor. I would think the signal to turn the heater on or off comes from the ECU based on engine temperature. 

[humph]

You had your car connected to a code reader?  Is the coolant temp sensor operating correctly? From experience of mine they're quite regularly not.  As you've found the wiring on our old cars can be dodgy so check power is getting to the sensors before replacing the units.

[Ian Hardaker]

I've connected to my laptop, and it showed that the intake air temperature sensor was reading bad. I've replaced that, reset the throttle cable lost motion, and wired the black and green wire to ground. It seems to be running better now! I've also bought a new engine bay wiring loom for it, but that looks like a big job to install!

Has anyone ever put a higher temperature thermostat in to allow it to stay above the magical 88 degrees? I was thinking of installing a 92 degree one.