ICV running with power off
 

Hi,

My 1988 3.2 Carrera Sport has just developed a new fault:

- Car runs fine when warm but stalled constantly when cold unless applying throttle
- Initial checks showed that ICV was dead (no buzzing).
- After removing it and some general checks on resistance etc I reconnected and it came to life but…
- Now doesn’t stop buzzing even when I have removed keys from the ignition. If I leave it plugged in the car now starts and idles well from cold.

So far as I can tell nothing else is powered and the car can be alarmed etc

First stop was to change the DME relay (spare on order), any other things I should check? I assume it could be a short?

Thanks

If ICV keeps buzzing even when key is removed, that means the ECU (Motronic) is still powered on, while it should be switched off. If you have changed the DME relay and the issue is still the same with ICV permanently buzzing, my guess is that DME relay terminal 86 gets 12V power from the anti-thieve unit while it shouldn't. Check voltage at this terminal. If you see 12V then your next check is the anti-thieve unit.

Plot thickens, went out to the car tonight, turned off immobiliser, dash lights on, fuel pump whirrs but no crank at all.

…went out to car to fit new DME and the battery is flat so looks like I have a parasitic draw (potentially the ECU if the DME is faulty).

If ICV is buzzing with ignition off, Motronic is on all night, no wonder why your battery is drained.

Address whatever keeps the Motronic running first. As I already suggested, DME relay pin 86 probably gets permanent 12V power while it should only get it when ignition is on. This 12V power is sent and managed by the factory alarm/immobilizer or aftermarket immobilizer if you have one.

All sorted, treated it to a new battery as it was getting pretty old, then replaced the DME and the ICV no longer buzzes.