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Vibration from engine all of a sudden

4614 Views 16 Replies 4 Participants Last post by  harryO
Today I started up my 2007 Saab 9-3. It normally starts up right away with no problems. Today when it started the engine was running very rough and had a lot of vibrations. After abuot 10 seconds the RPM died down and the engine eventually quit. I started it up again to find the same vibration. I thought that if I let it run for a couple minutes things may warm up (-10C outside) and the vibration may go away. No such luck. When I put the car in gear (automatic transmission) it felt like the vibration got 3x worse. Putting the car in neutral eased the vibration. Needless to say I didn't drive it anywhere and just left it.

Anyone with any thoughts on what this might be?


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Welcome to SaabScene Dico :).

DI is the Direct Ignition cassette at the top of the engine. If one coil has broken then that would cause the problem you describe. Very simple to change, just four screw and a connector.

CEL is the Check Engine Light on the dash. If there's a problem the ECU knows about then the CEL should show up. Connecting the car to a computer (Saab use a handheld one called Tech II) should be able to read any fault codes to find out what the problem might be.

Another possible culprit is the CPS (Crankshaft Position Sensor). It tells the ECU where the engine is in its rotation. If that fails you can get poor running until it fails completely and then the engine will just turn over. The ECU doesn't get a signal so it doesn't know the engine is turning. A bit fiddly to change as it sits at the front of the block behind the exhaust manifold (held in by a single T25 screw). I changed mine last year in approx 20 minutes.

When you crank the engine does the rev-counter show anything at all? If it does 'twitch' a little bit then the CPS might be OK. If there's nothing then the CPS is likely to have broken. If you have a multimeter you can check for resistance between pins 1 and 2 on the connector. It's the blue one to the right hand side of the throttle body (looking from the front). It should be 860 Ohms +/-90. Sometimes when they fail they are much higher than that (up to 1,500 Ohms).

It could also be something simple like an air leak. Check the various vacuum hoses for any splits or a loose connection.
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It's worth knowing that you normally don't get a CEL when the CPS starts to play up. The ECU simply does not get a signal telling it that the engine is turning (hence why it won't start). You normally won't have any fault codes either.

If it's the DI playing up then the ECU will normally store some codes (and flash the CEL if the problem gets bad enough). When mine went it showed plenty of misfires on one cylinder with a few on the other three (probably caused by the misfires on the bad cylinder). The CEL flashed a few times briefly.
Just make sure they use NGK plugs. They should be BCPR6ES (or BCPR7ES) gapped to 1mm. You can also use the more expensive PFR6H (IIRC) plugs but the BCPR plugs will be fine. Check your handbook for specific recommendations.

Do NOT let them use any other make and they MUST be resistor type plugs (hence BCPR). If they use ordinary plugs then you risk damaging the DI cassette. The DI cassettes were designed with NGK plugs as it senses the combustion through the plugs. If you use a different make then it won't work as intended.

Thanks for the update and glad she's working well again.
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