Saab 9-3 2007 1.8t misfires

[Martin Thomassen]

Hi,

I recently "inherited" this 2007 Saab 9-3 with the B207E with the Hirsch trim, when my brother in law and his family travelled abroad for an extended period. It does have fair share of issues, both most are straight forward.
One issue on the other hand puzzles me a little. The engine misfires, mostly audible in idle and more when the engines heats up. I haven?t driven it that much as it needs a hand of other repairs before it can be MOT?ed, but the misfires doesn?t seem very pronounced when driving the car.
I know my brother in law hasn?t kept the car very well services, so I pulled the spark plugs and found that the gap was off, so I swapped in a set of new ones pre gapped to 0.9 mm - no change what so ever.
I then checked the compression - which states 225 psi across all four cylinders cold.
Using a universal diagnostic tool I could see that the misfires were happening across all cylinders, but most severely on cylinder 3 and 4. I tried swapping the coils around, that that didn?t move the severe misfires to the other cylinders.
I then heard that I could be down to a broken balancing shaft guide, but I?m not entirely sure how this affects the timing of the engine, and I don?t really observe a whole lot of rattling from the chain side of the engine, though the engine isn?t exactly silent either. This is my first Saab, I?m mostly familiar with VAG cars and older rwd Volvos, so I?m not sure how silent this engine is supposed to be from the factory.
Does anybody here have any good suggestions how I should proceed from here?
Should I bite the bullet and pull the timing chain cover off the engine to see if something is off, or is there something else to look for first?
I do have a Tech II up and running now if that helps, but there are no codes stored.

Thanks!

Regards Martin

[Dave T]

Removing the timing chain cover and looking might be useful but I'm not certain.

[Martin Thomassen]

Just checked for vacuum leaks today with some brake cleaner. No indication of a leak.
I tried listening to the chains with a electronic stethoscope, but I don? really pick up any severe noise from this part of the engine.
The car starts fine from cold, and idle without severe misfires for the first minute, then the misfires get worse. If I then stop the engine and starts it again the misfires shortly disappears, at least for the first seconds while the engine runs with an increased idle
I wouldn?t be reluctant to replace the coils or chains if I just know for sure they where the culprit. I really hate replacing parts by mere (educated) guessing
I?ll try to measure the fuel pressure next, and the injector spray patterns as well.
If these seem fine, I guess I?ll have to take a look at the chain guides etc.