Removing blue temp sender - what does the ECU do?

[cheys03]

Hi there,

My current understanding is that when you unplug the blue temp sender the ECU enters 'limp home mode'.
What exactly does this entail? I believe the engine overfuels to reduce the risk of damage from the engine running lean, but are things like the timing/ignition advance adjusted?

Also when converting from a Mk3 CL to a std GT or G40 engine, do you need to consider different fuel lines to carry extra volume?

Many thanks

[PeteG40]

the fuel lines are the same, the rear fuel pump is different though.

Yeah, the lambda and blue temp sender adjust the fueling, if either of these have gone or unplugged it uses more fuel.

[quiksilver_jake]

i put both new in and my fuel consumption is nearly double what it was before and i have a heavy foot

[tdh-syorks]

yeah removing the blue temp sensor uses more fuel and the car violently splutters when starting up (needs lots of revs on the keep running), thats apart from it having a big piss when you remove the sensor (coolant).

[cheys03]

Ah excellent, thanks for the info.
Does the ECU also modify the ignition timing at all, or just the mixture?

[hayesey]

removing the blue temp sensor with the engine running puts the ecu into adjustment mode which basically means it stops adjusting ignition advance on the fly so you can set the ignition timing and idle.

If you start the engine with it unplugged or it has totally failed then the ecu goes into failsafe mode.  This means it uses basic fuelling map instead of reading various sensors and adjusting fuelling on the fly using them.  Digifant doesn't log faults so if you plug the sensor back in the fault clears on it's own when the ecu starts getting plausible readings from that sensor again.

[cheys03]

Fantastic information, just what I was after. Many genuine thanks everyone :-)