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Join Date: Jul 2008
Posts: 27
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Ignition skipping a beat?
My 78 SC runs rough on idle, and when driving at steady speeds. Not very comfortable. When accellerating it runs very well now, after these changes:
1. Put in a used distributor (From a 79). 2. New Permatune CDI-box. 3. Coil verified working. At first I was trying a rebuildt distributor, which fell apart inside when driving, so I can't trust that one even though it was put back together  I can hear, feel and SEE the problem, when using a timing light on idle I can see that it skips a flash when I hear the engine "skip a beat" and drop in RPM. Is this normal, or can I have some other part which is messing with the ignition? I know I may also have issues with slight air-leaks and possible uneven fuel flow (Low pressure, maybe, will have it measured), but these things should not cause the symptoms described above. Picture of the car, which is a daily driver from May to October, in snowy Norway  
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10-31-2009, 02:11 PM
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Join Date: Oct 2003
Location: London Ont Canada
Posts: 3,120
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You don,t mention replacement spark plug wires. I would suspect they could cause a cut out.
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1980 911 SC 3.6 coupe sold 1995 993 coupe 1966 Mustang Shelby clone 1964 Corvair Spyder Turbo gone 2012 Boss 302 |
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10-31-2009, 05:41 PM
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Join Date: Aug 2008
Location: sectors R&N, SE Pa
Posts: 3,117
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+1 on the wires - observe the engine in the dark for evidence of arcing.
Plugs ok? Maybe a cracked /dirty insulator?
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Dan '87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip Venetian Blue |
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10-31-2009, 09:21 PM
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Join Date: Jul 2008
Posts: 27
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Hi, and thanks for replies! I did actually change the plug wires last year, to some pretty good quality insulated ones. The plugs were also changed at that time. But I will certainly check both out!
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11-01-2009, 01:01 AM
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Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
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MCA put a new set of wires on his car and it ran worse, put the old ones back on and it ran better, put the new ones on, bad again. perhaps try swapping 2 plug wires, dont forget you have to move both ends. see if the problem follows the wire. also check the dizzy cap.
do you only see it on the one wire?
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86 930 94kmiles [_  _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold |
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11-03-2009, 04:51 AM
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Join Date: Apr 2003
Location: Maitland, Florida
Posts: 892
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Did you replace the distributor cap and rotor? I once got a cap with a bad carbon electrode in the cap.
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82 911SC Targa (05 Boxster S ) gone, but not forgotten 87 Suzuki GSXR-1100 1953 MG TD Mk II Last edited by SC-targa; 11-03-2009 at 07:02 AM.. Reason: spelling |
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11-03-2009, 07:02 AM
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Caveman Hammer Mechanic
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Check your primary wire, the one from the distributor to the permatune. It has a wire shield around the insulation, my insulation broke down and shorted the "points" signal.
eric
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1984 Carrera El Chupacabra 1974 Toyota FJ40 Turbo Diesel "Easy, easy, this car is just the right amount of chitty" "America is all about speed. Hot,nasty, bad ass speed." Eleanor Roosevelt, 1936 |
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11-03-2009, 04:04 PM
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