Maddening!

ruckman101 · Post by **ruckman101** » Mon Dec 15, 2008 2:28 pm

my #4 cylinder doesn't seem to be firing at low rpms, but kicks in at higher rpms. I don't get it. The spark plug is nasty black and oily looking. Is it a compression thing? Seems like there's consistent compression across the four cylinders when I spin the pulley. I just don't get it.

neal

bus71 · Post by **bus71** » Mon Dec 15, 2008 2:40 pm

Maybe a bad distributer cap or plug wire?

dtrumbo · Post by **dtrumbo** » Mon Dec 15, 2008 2:50 pm

I was thinking weak spark as well.

hambone · Post by **hambone** » Mon Dec 15, 2008 2:57 pm

Could be valve issues too. Do a compression test.

ruckman101 · Post by **ruckman101** » Mon Dec 15, 2008 3:08 pm

Swapped wires to no effect. Maybe the coil? Put a bosch blue on there awhile back, maybe back to the old one.

neal

glasseye · Post by **glasseye** » Mon Dec 15, 2008 5:23 pm

neal, those are symptoms similar to what I experienced when my condensor (capacitor) went bad right after I left Maupin, carrying.

bus71 · Post by **bus71** » Mon Dec 15, 2008 7:04 pm

I had a cold weather issue with our bug some years ago, fouled plugs etc. I discovered the heat riser was not working. It wasn't plugged, however. The muffler had rusted and failed in such a way as to plug the outlets. what made it hard to diagnose was that the heat riser pipe would work sometimes, then not. I think loose parts in the muffler would lodge in the outlets, then work loose. If you have a non-stock exhaust, some are not drilled for the heat riser. Don't know if this helps, but it was one of the oddball problems that frustrated me for awhile. Good luck!

Post by **Amskeptic** » Mon Dec 15, 2008 11:09 pm

ruckman101 wrote:my #4 cylinder doesn't seem to be firing at low rpms, but kicks in at higher rpms. I don't get it. The spark plug is nasty black and oily looking. Is it a compression thing? Seems like there's consistent compression across the four cylinders when I spin the pulley. I just don't get it.

Nasty black oily is a *mechanical issue*

You need to track down where this excessive oily is coming from.
You can have good compression and nasty black oily.
This normally suggests worn valve guides. A failed coked-up oil control ring can dump plenty o' oil in the combustion chamber and still give you good compression.

Check your compression with a gauge after adjusting the valves and inspecting each valve for proper seating. Let's see what we got after that first step.

Cylinder misfires in just one cylinder that has a dry-though-possibly-sooty-or-gas-wet plug is a different thing. . . the above suggestions are useful, as is pulling the wire to your dead cylinder out of the distributor cap just 1/4" at idle to see if you can compel it to start firing. If you bought Bosch plugs recently for this engine, if they are the Made In India plugs, I have had annoying and unusual quality lapses, like leaks between the white cenramic and the metal shell.'
Colin

RSorak 71Westy · Post by **RSorak 71Westy** » Tue Dec 16, 2008 9:06 am

Replace the plug as temp fix, if it fouls again, replace it with a hotter plug, until you fix the mechanical issues.

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