Misfire! Saab 9000CS LPT Auto 1993

Have the HT leads been changed?

Doesn't have leads, it got the Direct Ignition fitted. I've read that these buggers always go but it was swapped with one from another Saab but it hasn't made any difference.

No HT leads, uses a DI unit.

This would be my first suspicion - the DI unit. Get it checked out, or swap it for a known working one.

Next thing would be the injectors. Check that non of them is sticking.

Ah, you've already swapped it.

Check the injectors. When it stops working, remove the whole rail, point into a container, and turn it over. Do they all spray.

musty read properly next time

Will a compression test be ok to determine if it's head gasket?

If it was an 1989 - I would say it sounds almost like the engine management system is cutting off the fuel upon interpreting a knock.. Which isn't to say there is a knock - but - it may be reading one on a short or some other engine variance (timing - water in the fuel)..

Is the management system less sensitive or more comprehensive on the

Sounds like primary ignition breaking down when hot- does the rev counter begin acting up when the engine does? Have a good poke around at the CAS and wiring plug. Get some freeze spray (computer or plumbers shop) and and spray it onto the CAS next time it plays up when hot. I think you will find you are loosing spark which is the root of your problems.

Tim..

The DI unit was my first suspect, but the OP says he's swapped out the DI for a known good one.

But I didnt mentiont he DI unit- we know he's already swapped it. I was talking about the primary trigger- the CAS.

Tim..

Sorry, my mistake - I didn't recognise CAS - do you mean the crank sensor?

Today I had a look at the car for myself and to make absolutely sure it wasn't the Di unit our local saab dealer kindly sold us a brand new unit (200ukp) with the option to return it for a full refund if that wasn't the fault. Also put in a new set of NGK sparkplugs and set the gap to