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Old 04-18-2017, 11:30 AM   #1
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Question White smoke, misfire, knocking, rough idle after sitting for 3 weeks. Help?

You all were awesome helping me diagnose my bad wheel bearings. Hoping you can give me some advice about a new problem I had this morning.

I have the opposite problem of most Boxster drivers, in that I live in Arizona, so the winter is prime convertible time and I park it in the garage during the summer.

After driving it all winter with no issues at all, I decided about 3 weeks ago it was time to put it away for the summer. Before putting it away, I changed the oil and let the engine run for a while to ensure no leaks. No problems.

This morning I decided it would be cool enough to go ahead and drive it to work. It took a long time to crank before it started. Immediately after starting, extremely rough idle. White smoke for a few seconds. There was a loud knocking-like sound as well as what seemed like misfiring. No CEL. After about 30 seconds of idling, it seemed to recover from whatever the problem was, the idle smoothed out, no knocking sound, no misfiring. Drove it into work without any further issues, no smoke, no weird sounds, full power.

What do you think? Air oil separator?

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Old 04-18-2017, 11:34 AM   #2
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I should add: 2001 Boxster S, 45K miles
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Old 04-18-2017, 11:38 AM   #3
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Symptoms would seem consistent with a bad AOS. The smoke from oil leaking into the intake manifold. The knocking from hydraulic locks in the cylinders, or possibly preignition. I would worry a lot more about the knocking than the smoke.
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Old 04-18-2017, 12:43 PM   #4
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Could be fuel fouled plugs from excessive cranking which cleared after idling for awhile.

Initial hard start might be the cps if the tach was not bouncing during cranking.

Could also be the first sign of a failing fuel pump or relay.

Regardless, as it has been said before Porsches will get even for letting them sit.
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Old 04-18-2017, 02:46 PM   #5
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A small cloud of white smoke particularly after sitting is not uncommon. I've seen it with mine after sitting. I've also had mild bearing rattle at startup, and that is with 20k miles on the bearings. Not too sure what to say about the rough running. As it cleared up there's no real root cause. If it were me I'd continue to drive it for a few days to see if it repeats. If it doesn't give it a few weeks, if still nothing, a few months. Then it will be driving season again and your problem will be solved.

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