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  #1   IP: 152.121.18.98
Old 05-09-2008, 02:21 PM
powersgeoff powersgeoff is offline
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Unhappy Runs better when wire pulled off plug?

My A4 has two cylinders that run better when I pull the wire boot off the plug (break the metal to metal connection) and force the spark to jump a gap. With the boot just sitting on top of the plug the engine runs GREAT. Push it all the way down and make a connection it'll start missing. Does this on cylinders 3 and 4.

Makes no sense to me. Any Ideas?
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  #2   IP: 24.61.154.105
Old 05-10-2008, 05:37 AM
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jhwelch jhwelch is offline
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Does it "run great" when the plug wire is totally disconnected? I've
seen other postings where the exhaust gasses from four working
cylinders caused so much backpressure with a clogged exhaust
system the engine ran poorly. Dropping it down to three working
cylinders "solved" the problem. So maybe your exhaust is clogged
or an exhaust hose has failed internally.

-jonathan
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  #3   IP: 38.102.16.123
Old 05-10-2008, 08:12 AM
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Don Moyer Don Moyer is offline
 
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Our normally reliable experts from the Pertronix Company tell us that when a plug fires with the added resistance you induce when holding the wire a short distance from the plug but not when the wire is actually connected, the problem is a path of low resistance within the plug that is easier for the secondary discharge to follow than jumping across the .035" gap. The pathway of low resistance is usually some electrolytic build-up on the center porcelain post. The added resistance induced by holding the plug lead a short distance from the plug allows the secondary discharge to build up sufficiently to jump the gap of the plug before detouring around the gap (down along the center post). The solution is to thoroughly clean or replace the plugs.

Don
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  #4   IP: 71.179.188.109
Old 05-10-2008, 09:16 AM
powersgeoff powersgeoff is offline
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Talking Runs better when wire pulled off plug?

The engine does not run better with the wire complely pulled away from the plug. With the wire on all the way the plug misfires occasionally. With the wire off (metal to metal connection broken) and a short gap induced the park will jump the gap and the plug will fire 100% of the time; i.e., "runs great".

I've cleaned the plugs many times with no effect. I'll go down today and try new plugs.

Thanks for the ideas. I'll let you know how it goes.
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  #5   IP: 152.121.18.98
Old 05-12-2008, 08:28 AM
powersgeoff powersgeoff is offline
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Thumbs up

New plugs did the trick. All four cylinders firing. Runs great.

Thanks
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  #6   IP: 66.161.32.165
Old 05-12-2008, 10:21 AM
luvmyi36 luvmyi36 is offline
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Lightbulb

It's amazing to me how clean my plugs have been before, yet the motor still runs poorly... Change the plugs and all is well. Lesson learned? Keep a spare set of plugs on the boat!
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