740 poor running and stalling

[Laird Scooby]

Originally Posted by Beadybc

Yeah you're correct about the MoT part, completely forgot about that screw you mentioned before I was struggling to think of new ways to adjust the mixture. Cold start valve came up when searching for a fix but no where did it say how to test whether that was the problem so cheers for that.

Just to be clear, the test i suggested of simply disconnecting the electrical plug from the cold start injector is only a very simple test and won't cover all eventualities possible with it, however it should yield enough clues to help with the rest.

Hopefully it's something fairly simple from here, most likely is it started misfiring before it was laid up and has got worse since. They probably tweaked the mixture screw to get it through MoTs before that so it's running as rich as anything now. On my 760, i had similar (although that's LH-Jetronic) because my injectors were dirty. When i replaced them with some Vauxhall Omega V6 injectors (cross-referenced to the Bosch replacements for the OE injectors, then found the GM V6 used the same injectors!), the performance was vastly improved, however the idle CO shot up from ~1% to about 9%!

I tweaked the mixture screw on the MAF to get it back to where it should be and still had improved performance, response and economy, hence my suspicion about what's happened with yours.