2006 saab v6 misfire / overboost

Maintenance/Repairs
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1

The car: 2006 9-3 aero V6 turbo - manual transmission - 110k miles

The problem:
When turbo boost pressure gets close to the red under acceleration - either with high rpm: 3rd gear/50mph and max throttle OR low rpm: 6th gear / 45mph and max throttle - engine cuts out abruptly, and ‘stutters’ until you ease off the gas. Sometimes this triggers ‘limp home’ mode, where it will not apply any boost pressure again until car is restarted. Sometimes check engine light is sometimes triggered, with one of either: cylinder 5 misfire, or overboost (turbo pressure) codes.

The diagnosis:
Trusted mechanic has replaced ignition coil (twice to be sure), swapped spark plugs with cylinder 4 (still sees issue in cyl 5) and now thinks it is either a bad fuel injector (from what I hear these are very reliable) or a major ‘valve’ issue which would entail a presumably very expensive head rebuild.

The questions:
Is there anything else that could cause this? Before we eliminate the injector and Im presuming looking at a head rebuild. is there anything else to check / pray for? If it does turn out to be some valve issue, could the car be driven for a very long time as is, or would it deteriorate further?

2

Howdy. I know your post was seven years ago, but I just came across it. I have the exact same problem you describe, on a 2003 Saab 9-5 Linear. Did you ever get an answer? I’m hoping everything worked out for you. I haven’t solved mine yet.

3

Oh for sad timing, as my precious saab sits rotting in my driveway after being hit last summer.But that was a terrible situation with the overboost. I was convinced it was a header-job (prohibitively expensive) and drove in limited fashion for some 30k miles before resolving fully with proper ignition coils.

Do NOT I repeat: do not! go for aftermarket coils. Those things are expensive, but you have to go OEM on them, as that was what was causing the whole issue that plagued me: I replaced coils, used aftermarket parts, and then in all subsequent analysis, removed them from consideration because we just did them. If you are in the range (90-100k miles) where they start to go do them all, get it over with save yourself the frustration.

Good luck! Saab on!