Holden Epica Engine Problems

Seems like you might have two problems here. The first is that I suspect you’ve may have fried the computer in the Holden in the process of jump-starting your other car. Jump-starting a modern car with on-board computers is something that should only be attempted by somebody who is a specialist. There’s a specific technique that goes beyond simply hooking up the jump-cables and hoping for the best. It’s all too easy to send a voltage spike through the car and send the computers into melt-down. That would explain why the car will not restart.

As for the milky oil and the sludge under the oil-filler capo, that sounds unrelated but still serious. A blown head gasket can lead to this exact set of symptoms and it occurs when the engine’s coolant is allowed to mix with the oil (and vice-versa). Sometimes in these colder months (particularly in Tassie) it’s not uncommon to get a small amount of frothy, grey muck under the oil-filler cap, but not a huge amount. And if the oil on the dispstick is also covered in oil contaminated with coolant, then you’re looking at a new head gasket at a minimum.

I’m not sure I agree that all modern Holdens were problematic, but the Epica, which was really a Daewoo (it was built in South Korea) with Holden badges, is definitely on the suspect-reliability list.

As it is an intermittent problem it’s hard to be definitive, but I would suggest you look at the fuel system, and check for a faulty electrical connection that could affect the operation of the fuel pump or injectors.

Change the belt as recommended at six years. Belts deteriorate with age as well as kilometres and you don't want to risk the damage that might occur to the engine should the belt fail.

It does sound like it's an electrical or electronic problem, because when it happens the car is going into limp home mode, which is when you lose power. These problems are not unusual with today's cars, which rely so much on electronics.

The warning lights are indicating there is a problem with your car’s engine/emission system, and it needs to be checked by a mechanic to determine exactly what it is. By all means check the oil level in the engine, by removing the dipstick and seeing the level indicated on it, but I doubt that is the problem.

The 5w-30 is often used and is ok as an alternative to the factory recommended oil.

It sounds plausible that the wiring harness could be damaged and needing replacement. You can get your answers from Carsguide.com.au.