Voltage issue on ecu

[jimbodabong]

FTO GX

I currently have no rev counter and the car likes to cut out approaching junctions after a few miles cruising but only when the A/C is on. We gave it a good check round at the garage and found that the idle becomes quite rough when the main radiator fan activates and its worse when the A/C is on too (more so than would normally expect). We then popped it onto a gas analyser, we found that the CO shot up when the fans were running and didn't really settle back down. We then checked the voltage of the ECU circuit at the fusebox and found a strong 13V but it occasionally spiked down to 6V when a fan came on.

My uncle who has years of experience working on classic Jags but isn't an auto electrician suggested that the voltage drop could cause the ecu problems possibly causing the injectors to allow the engine to run rich, hence the odd staul and sky high emissions.

I can easy take out the clocks/IFS and have a check them over using the brilliant guides I found on here . However I was hoping someone could give me a few pointers on where to start looking.

Thanks in advance

[brccrx]

Clean your throttle body and icv (step motor), or perhaps the icv need replacement.

When there's extra load (ie A/C on, second fan kick in, etc, etc.) the signal being send to ECU to rise the revs slightly, this mean:
inject extra fuel, same time the icv should open a little more to aloud more air being added as the extra fuel is injected, but that not happening causing high CO read out and voltage drop under load if You understand?

[jimbodabong]

Will give that a go this weekend, high CO and spiking voltage on increased rpm also though.

[brccrx]

Only when load added?

[jimbodabong]

Usually when under load but not exclusively, we noticed the jump in CO when the fan came on, however it doesnt settle back down when the fan goes off. This happens at idle and at a holding rpm.

[brccrx]

I see. Maybe alternator voltage regulator start giving trouble? Also i would suggest trying to lent gr/gx ecu and swap it with the one you have and test for voltage trops again.