Did this just start happening all of a sudden or get worse over time ? Are you handy with a wrench ? -

Some easy things first....

Check the wires going to the coil - if they have vibrated lose it acts about like this.

Pull the Carb bowl and main jet if it's plugged it acts about like this.

Then fun things like the slide is hanging... Ing module and such - bet it's not anything bad

The heavy backfires are not normally caused with air starvation - a rich condition - but it certainly can - I'd expect you to be fouling the plug if that was the case  

First thing I'd do is drain the carburetor float bowl. It's very easy. There's a drain screw on the bottom of the bowl. Stale gas, dirt, or water in the float bowl will cause some problems. Use "prime" on the petc0ck to refill the bowl if you want to drain it more than once.

shuki wrote on 04/06/08 at 20:36:09:


That's a great one to know. I love it when people report back their final 'fix' as making mental notes of those can save other folk a lot of hassle later.  

BTW, I used to work at a detail shop when I was about 16. My job was to wash/steam clean the engines. Even though we wrapped the distributor and coil in plastic or foil, and tried to avoid spraying those areas directly, about one of ten cars would require a new distributor cap, rotor and sometimes wires before they would run right again. Sometimes some WD-40 sprayed in the cap would fix it. If that didn't work, we just started with the cap and rotor; then replaced the wires if we had too.  

I'm betting even though you didn't spray the engine directly, you got water on the plug wire, and once a spark jumps through a weak spot once it becomes the new 'path of least resistance' to ground; causing intermittent firing.