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I'm going to subscribe and see what I can learn. I have an 80 SC and have the same problem, but it goes along with a fluttering idle. Occasionally I can get a perfect idle. Most of the time, I get a fluttering idle from 1100-1500 RPM that sounds like the engine wants to die and there is some knocking associated with it. Then suddenly it will settle down and idle perfect.
I think I've solved all the vacuum leaks, but I have one more breather hose to go - the one that connects the air metering plate boot to the oil dry sump. It's ancient and in bad shape. I confirmed good pattern and balanced injector flow. This weekend I'm going to check fuel pressure. I"m also going to check timing and pull the plugs to see what they say. Bad spark is worth checking. I'm also going to look into how to test the O2 sensor to see if it is mis-behaving.
I have a good independent mechanic who specializes in air cooled Porsche, and he's confirmed in the past that cyl #2 is basically going along for the ride. He thinks that a dead cylinder will cause irregular pulse in the intake and confuse the idle. So the last step after troubleshooting all the tune-up items is to drop the motor and have him re-ring Cyl #2 as long as the heads are serviceable. May be time for a complete top end. Then again, at 260,000 miles, it's time for the whole thing to be rebuilt.
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10-22-2013, 09:17 AM
