Thread: CIS operation
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930turbo 930turbo is offline
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Join Date: Jul 2006
Location: Valrico Florida
Posts: 200
CIS operation

I spent about a year fiddling with my CIS in an attempt to resolve a rich at idle condition. I was about to commit to a fuel head and WUR rebuild when by chance I discovered the real problem. The trigger wire plug from the distributor had a bad connection. I replaced this wire and completely rebuilt the wiring harness on the engine during the rebuild 7000 miles ago so I assumed there would be no issue there. I pulled on the wire while the car was idling and it died. When I checked inside the plug, it was green. Apparently it got wet somewhere along the way. I cleaned the connection and the problem is solved. The signal from the distributor weakens as the engine slows. It had a mis-fire at an idle that sounded like an old small block Chevy with a large cam. It smoothed out as soon as you increased engine speed above idle. The over-rich condition was caused by the asymmetric mis-fire @ idle. If your car doesn't sound like a 911 SC at idle, check your ignition. My lesson learned, don't necessarily blame your CIS.
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'77 930 turbo Garretson I/C 1 BAR spring, (2) '82 Triumph Bonneville Royal Wedding Edition
Past rides: '74 914 1.9 liter twin plugged track car, '83 928S, '87 924S, '75 911S w '78 ROW 3.0, '72 911T, '70 911T and various other insignificant domestic examples. Happiness is a grey tailpipe! Turbo lag......it's worth the wait!
Old 01-29-2009, 11:50 AM
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