Peculiar loss of power—no codes

[IceBlue]

I am wondering if any of my fellow 9-5 lovers have had a similar experience. I have a 2007 9-5 Aero. It currently has 128K miles on it.
Several months ago, I was on the highway doing about 60mph. I had cruise control on. Suddenly, there was a loss of power, the car vibrated and shuddered, and the "check engine" light came on. It lasted less than 10 seconds and then, with a lurch, acceleration resumed and the car again drove normally. I parked at home and the next morning, upon starting, the check engine light was no longer on. I went to my mechanic who plugged in the code reader but the car showed no codes of any kind. This was months ago (8-10 months I'd guess) and the car has driven normally since. About 2 weeks ago the same thing happened and this time, instead of being solid, the check engine light flashed on and off. Once again, after a few seconds, the car resumed acceleration and the check engine light went off. I again took the car to my mechanic who, again, found no codes. He did say that he had detected some episodes of misfire in the first cylinder (apparently the code reader shows this) and replaced the spark plugs. He said that it was possible that the misfiring due to old plugs had caused of the problem. It is disconcerting, to say the least. I replaced the ignition cassette in July 2017 (I'm sure you all are familiar with that little issue) so I am confident that that is not the cause.
Has anyone else experienced this issue and, if you have, gotten to the bottom of it?

[sgould]

My 2007 car hasn’t done this, so all I can do is guess.

I’ve only ever seen a flashing engine light twice in 16 years I owned various 9-5s. Once was when I ran out of fuel (with the display showing 15 miles to empty!!); the other was when the ignition cassette failed.

Something intermittent could be a loose wire or a blockage.  Check that the earth cable from the ignition cassette is attached.  It screws to one of the bolts on the thermostat housing.  Often forgotten if the thermostat is replaced. 

Any rattles from the fuel tank?  The baffles in the tank come lose and move about, but usually only affect the level gauge.

I’ve seen one instance of the rubber inlet pipe attached to the intercooler collapsing, but that was on the overrun.

Fuel filter changed?

Turbo  wastegate sticking open?

It’s a difficult one...

[IceBlue]

Thanks for the suggestions. I actually asked my mechanic (a Saab specialist) about the fuel filter and he said that my car ('07 9-5 Aero) doesn't have one.

[sgould]

Well I have the same car, and I've paid for the filter to be changed.  I believe that it's near the fuel tank at the side of the car under the rear RH door.

Are you in the USA?  It's a different system there.

[IceBlue]

Thanks. Yes, I am in the USA. Is it possible that a 9-5 Aero sold in this country does NOT have a fuel filter?

[sgould]

Yes. It's likely.  The parts list marks the filter as (not USA and Canada).  And I can't see another one.  The fuel pump is hidden in the fuel tank and is also shown as different for the USA/Canada, as is the tank itself.  The filter may be part of the pump, but I don't know.

[ade wilkins]

i had this on an og93, in my case it was a cracked spark plug, but i have been told that it could be one of the sensors in the exhaust... not sure which one though

[ade wilkins]

just been told it could also be the MAF meter

[sgould]

A faulty MAF meter usually gives a P0100 code...

[twosaabs]

Just coming back to this one again. Aero had a CEL issue this weekend but I had to drive back from York. I didn't have my code reader with me but the car seemed to be fairly OK, just a little bit ragged and drove back South 200 miles with no obvious problems. Hooked up this morning but code reader couldn't find a code number so I cancelled the erro and CEL went out.

But it's come on again, and still can't read a code. I think I'll have to toddle off to find TECH-II chap to get to the bottom of it. I suspect that it's a misfire. She's coming up for a service, so she'll get a new set of plugs anyway. Watch this space for further developments.

[phoenix]

Your car does have a fuel filter, but it is different from other markets which use a paper one. Yours has a carbon based one. Perhaps it never needs changing? I can't see anything in the service schedule to say it does.

[carrera]

It's very strange to have a CEL with no code stored.

You can have a situation where a CEL is thrown, but it gets cleared after so many "good" ignition cycles. I have seen that myself. In that situation there is no CEL to clear, but maybe the snapshot remains accessible through Tech II.

[twosaabs]

That's a thought. I may start up and as soon as CEL comes up, shut down and see if the code is stored.

[twosaabs]

Tried that and I have P0171. Anybody any ideas?

[carrera]

You can read the codes while the engine is running.

P0171 seems to point at quite a lot of things and seems to relate to the engine running lean.

It's suggested to check crankcase breather system first and then fuel pressures / MAF. From what I have read it indicates a disparity between the fuel requirement measured by the MAF and that measured by the manifold air pressure sensors.

I think I had that one, alongside many others, when I blew the side off my intercooler. That's when I found out the engine would run better with the MAF electrical connection disconnected.

Others will probably give you better help, hope this at least gives a little pointer in the right direction.