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Discussion Starter #1
Hi Guys - 2007 Cayman with 92k miles, and just this week, while stopped at lights, the engine will go from idle (+-700 rpms) and increase up to 1,600 rpms, then fall back down to 700, then go back up, or stay up around 1,600 until I hit blip the throttle.

Temp gauge appears to be operating normal, and this is happening well after the car is warmed up.

Durametric Enthusiast Version showed no codes. I erased all codes anyway, and no change.

Any idea what's causing this?


Thanks!
 

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It usually indicates a vacuum leak some where. There are a few methods to find a vacuum leak, but I've always (carefully on a COLD engine) used carb cleaner to locate the vacuum leak. Hopefully others will chime in, but that'd be my guess.

**I realize there are quite a few possibilities for a surging idle (i.e.: PCV needing replacement, TPS, plugs, etc...). I just mention a vacuum leak because that always seemed to be the most common issue with my previous (non-Porsche) cars.
 

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Owen, there is a vacuum diagram on the engine cover. Fortunately there are not many vacuum lines on this engine so if that is the problem hopefully it will be easy to locate. There is one going to the scavenge pump on the front of the engine on cylinders 4-6; two connections under the intake runners; one that goes to the throttle body; one that goes to the resonance flap. There may be one more but I think that is all of them. The diagram is somewhat hard to read but some of them cross over to each other (intake runners) and there is a 3 way T connection as well. Hope this helps.
 

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Discussion Starter #4 (Edited)
Well....

Started it up after work, larger cloud of smoke than normal, but not too much more...

Started driving home on the George Bush, and I see smoke from the back (same color as the random startup smoke) during traffic start/go.

Wonder if it's a concern enough to be able to make it home, and then it starts getting REALLY bad, smoking up all lanes.....

Pull off and the engine dies, push in the clutch and coast into a WalMart parking lot (that was lucky).

Engine won't turn over. Towed it to a local shop - they think it's the AOS, and maybe seized due to oil in the cylinder. They don't think it's catastrophic, but they have seen one that was...

Good thoughts my way please!
 
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