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View Full Version : Predetonation?





BK Butler
04-29-2000, 12:56 PM
I have a very nice 1982 911SC with just over 100K miles. (K-Jetronic w/lambda air sensor) Since I first bought the car @ 77K miles, there's been a persistent problem. Between 3K and about 4.5K RPM, there is a sharp sound like predetonation that's mostly heard on the drivers side. This occurs most during 1/2 to full throttle acceleration. I've had the car timed and tuned several times by the local PCA racing guru, and use the highest octane gas without any change. This is NOT a typical timing problem because the car works fine even hot and under load up to the RPM range mentioned. It may be a bad injector(s) -my next project- or carbonized heads because it's worse when the engine is warm. The situation gets much worse at lower altitudes (Phoenix AZ or Houston TX). Here in Denver, it's quite drivable, but sometimes it would be nice to rev it up without fear of ruining something. A very frustrating problem. Also, at the lower altitudes, the RPM increases to about 2,500 unless I back off the idle screw. Any ideas would be greatly appreciated!

Matt
05-11-2000, 08:14 AM
This problem does not ring any bells. I am pretty familier with SC's and I'm not sure what you are hearing. Without being able to hear the noise I couldn't even guess. Sorry I can't think of anything it could be.


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