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2005 9-3 Aero B207 Misfiring, Cutting out, Fouled plugs

337 Views 10 Replies 8 Participants Last post by  MPLsaab
Hi folks, this might be a bit of a novel so apologies! Going to try to give the full picture here..

My 9-3 has had an intermittent cutting out issue for ages where it would just go dead when slowing down. I thought it was the CPS and a Saab garage confirmed this as it was throwing the relevant code when live scanned. So a new sensor was installed. It ran fine for a week or so then it started to cut out again, only this time it would start up straight away which it didn't before the CPS change..

Also the idle has been getting rougher all the time as if there was a slight misfire when up to temp (not when cold) along with a strong raw petrol smell.

The cutting out got more frequent and the idle worse so I started to look at other things, cleaned the throttle body (which was filthy) and yesterday, the MAF sensor.
Seemed to be running much better until I took it on the motorway and at about 80 it started to misfire violently. I pulled over on the hard shoulder and as I slowed down the engine cut out.

I got recovered but then the breakdown truck broke down (yes really)
So rather than wait another 3 hrs in the cold I decided to risk driving back and the car jerked and sputtered the 2 miles off the motorway cutting out repeatedly.

Today I looked at the plugs and found that they are all filthy and sooty/oilly and worryingly cylinder 3's plug wasn't even screwed in properly! Maybe a thread or two in and the ground electrode is broken off! (see pic)

Took it out for a test with the new plugs and now the turbo is whining really loudly and the car feels very underpowered in low gears!! WTF!! Surely my turbo hasn't died as a result of this?

I feel like there's a clear picture here and I'm just not seeing it. Any thoughts/ insights gratefully received!

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Please tell me that electrode did not break off into the cylinder.
Whats the status on the coils?
Sometimes when the T8 Ecu fails, the injector drivers will stay on causing it to dump fuel into the chamber which can foul up the plugs like that.
 

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....the only place the electrode can break off is in the cylinder.... Interestingly when a spark plug is seized the shop tool to remove it purposefully breaks it, obviously the ceramic bits can't just be taken out with a magnet but the tip could be extracted by magnet if it hasn't been ejected already. If you're real lucky that occurred spontaneously with compression intact.
 

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Discussion Starter · #7 ·
Thanks for the replies folks.. Indeed the electrode did break off into the cylinder. As the car has been driven quite a number of miles in this state before I realised, I'd assume there was no catastrophic engine damage. However I wonder if it might have made it's way to the turbo, hence the noise..

Codes were only for a random misfire across all cylinders when the recovery guy scanned it. I have now taken it in to a Saab garage so will get the full lowdown shortly!
 

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Discussion Starter · #9 ·
Please tell me that electrode did not break off into the cylinder.
Whats the status on the coils?
Sometimes when the T8 Ecu fails, the injector drivers will stay on causing it to dump fuel into the chamber which can foul up the plugs like that.
The coils are actually alright. I did a compression test just out of curiosity and the numbers are pretty good so hopefully no significant damage to the bores/pistons
 

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Codes were only for a random misfire across all cylinders when the recovery guy scanned it. I have now taken it in to a Saab garage so will get the full lowdown shortly!
Do not be surprised if TECH2 founds bunch of real DTCs. Generic reader (what recovery guy usually have) will not read all DTCs.
 
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