#3 Cyl. Spark Plug Fouling - Alfa Romeo Bulletin Board & Forums
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post #1 of 5 (permalink) Old 06-07-2010, 05:22 AM Thread Starter
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#3 Cyl. Spark Plug Fouling

Can anyone suggest to me the cause of my #3 spark plug fouling on my fuel injected Spider? At an idle it runs rough. I get a noticable drop in rpms when I remove the wires from 1, 2, and 4, but non when I remove #3. At higher rpms it seems to run ok. I have replaced the plugs with hotter ones. It still fouls. Any suggestions???
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post #2 of 5 (permalink) Old 06-07-2010, 06:24 AM
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What model year Spider? If EFI it could be a faulty fuel injector (stuck open) or an intake air/vacuum leak (the extra air from a leak will cause the computer to compensate by squirting more fuel. If the leak affects other cylinders more than #3 then #3 ends up 'rich' because all the injectors squirt equally - the computer does not control them individually.)

If it is SPICA then I don't know much about that.

- - Eric
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~ 1984 Spider Veloce ~
- -~ 1981 GTV-6 ~
Mebane, North Carolina

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post #3 of 5 (permalink) Old 06-07-2010, 11:36 AM
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I would start with a compression check. A weak cylinder can foul the plug with oil and, or fuel.



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post #4 of 5 (permalink) Old 06-07-2010, 11:48 AM
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I would start by testing the wire itself. I've had one wire from a set go bad. swap wires with another cylinder and see if the problem follows the wire or stays with the cylinder.

[FONT="Century Gothic"][B]Bob Farace[/B]
[COLOR="DarkGreen"]1971 Alfa Romeo 1750 Spider Veloce[/COLOR]
[I]Director, Connecticut branch, Scuderia Non Originale[/I][/FONT]
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post #5 of 5 (permalink) Old 06-07-2010, 02:20 PM
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I think you have an electrical problem, not a fouling problem. New distributor cap, new wire, and new spark plug.

John Stewart
74 Spider
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