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Discussion summary
YOUR RESEARCHLeft bank not firing, oil air seperator?
Leading reported evidence
Run previously
Performed · outcome unconfirmed
No successful repair reported for this finding.
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Performed · outcome unconfirmed · Original poster
(almost looks like there's an oil tide mark on the piston) I don't know the history of the issue of how the car ran previously.
Leading evidence: 'Run previously' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'sensible next step' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check alignment marks' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed
It turned out the cam chain had snapped on the non firing bank and the cam was stopped (it still ran though, which I was amazed at!).
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Performed · outcome unconfirmed · Original poster
I think there is fuel and I've tested for a spark, all looks ok.
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Suspected cause · Original poster
I've not done a compression test yet, probably a sensible next step.
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Suggestion · Original poster
To confirm, the inlet camshaft is rotating, I can see it's out of time by checking the alignment marks with No1 at TDC.
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Unsuccessful attempt
I checked the plenum, that's certainly where the oil is coming from. Unfortunately my troubles are not solved, I did a compression test today, left back doesn't have compression on any of the cylinders.
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911uk: 1 discussions
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I have a 996 project that's causing some issues.
The car will start and idle but only on 3 cylinders, the left bank is not firing at all, headers are cold. You can imagine it's a little lumpy. As soon as throttle is applied the engine cuts out. I think there is fuel and I've tested for a spark, all looks ok.
When removing a plug from the non running side, it's wet with oil. I've looked in the cylinder and there's a decent puddle of oil in the bottom. I've not done a compression test yet, probably a sensible next step.
So, the question - can a faulty Oil Air Separator fill the cylinder with oil? The car has been stood for some time, I wonder if this has any bearing on the issue. (almost looks like there's an oil tide mark on the piston) I don't know the history of the issue of how the car ran previously.
Thoughts much appreciated.
Take your throttle body off the plenum and see how much is in there going in to either side of the engine.
In here:
https://www.pelicanparts.com/techarticles/Porsche-996-997-Carrera/09-ENGINE-Air_Oil_Separator/images_large/pic07.jpg
Thanks Alex
I checked the plenum, that's certainly where the oil is coming from.
Unfortunately my troubles are not solved, I did a compression test today, left back doesn't have compression on any of the cylinders. The engine starts to build compression then seems to vent it through the intake plenum............very strange.
It has the feel of the inlet camshaft being out of time? Can this happen without a failure of a chain or IMS bearing? The engine will run on 3 cylinders which suggest to me nothing has catastrophically failed.
Has anyone experienced this before?
Have you confirmed that the cam on the non firing Bank is rotating?
I saw a 996t once which was running on three cylinders, it was also venting backwards through the inlet with occasional backfires.
It turned out the cam chain had snapped on the non firing bank and the cam was stopped (it still ran though, which I was amazed at!).
Owner was lucky as it had only bent 2 valves!
Not saying it is this, but symptoms are similar!
Sounds like the timing is very suspect. You can pop off the green head plugs and see the cams turn while cranking/turning the motor to see whats up.
Sounds like the engine needs to be pulled.
Thanks for your thoughts,
To confirm, the inlet camshaft is rotating, I can see it's out of time by checking the alignment marks with No1 at TDC. Exhaust camshaft is correct, inlet cam shaft approx 30 deg out.
I wonder if the camshaft has moved in the vario cam actuator? (The part on the end of the camshaft) Is this possible, does it have a key way? On the assumption it's somehow moved, can it be retimed in the car? Has anyone tried this? I think I can gain access by dropping the engine a little.
That said, slightly concerned it'll move again and I might not be so lucky next time, no valve to piston contact had occurred on this occasion.
Certainly a strange one,
On a 5 chain engine the exhaust cam is driven directly by the IMS and the inlet cam is advanced 24 degrees when the variocam is activated. So 30 degrees does sound suspect. Although an engine will run with the variocam in either position.... maybe best to check the procedure for setting the timing, as there are bolts that allow the timing to be set which I guess may have come loose?
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