1966 L79 Wild Bucking

[Marc K.]

I noticed an occasional engine sputter during summer driving season. It got slightly worse each time I drove. Now, I can't drive it at all. I was lucky to get it back in my garage. I can start it, but it won't hold an idle unless I keep giving it gas. I took the carb to my carb guy and he said it looks fine. I tested the coil and it failed one test so I replaced it with a NOS one. I re-seated the spark plug wires. I had the fuel pump and fuel sender units rebuilt. I replaced the fuel inlet filter. I'm still thinking carb. Fuel or ignition? All opinions are appreciated.

[Keith B.]

Re: 1966 L79 Wild Bucking

Did you do the basics of checking the timing, dwell, points, check the rotor and cap for cracks?

[Marc K.]

Re: 1966 L79 Wild Bucking

Unfortunately, I can't hold an idle to check the timing and dwell. I turned both mixture screws to 1.5 turns open. I initially thought this was the problem. I pulled the distributor cap off and all looks good. It had a complete tune-up 1,100 miles ago that included new plugs, plug wires, distributor cap and rotor, points, condenser, dwell and timing adjustments. The carburetor was rebuilt not too long ago.

[Keith B.]

Re: 1966 L79 Wild Bucking

Have you checked for vacumn leaks. Take a mity vac and see if the vacumn advance can will hold vacumn

[Jim D.]

Re: 1966 L79 Wild Bucking

Have you checked for vacumn leaves.

I agree. After all, it is fall and one one must check for leaves.

[Rich G.]

Re: 1966 L79 Wild Bucking

Had similar issue with my 68 BB. Turned out to be a bad coil wire, the high tension side. It’s a long shot, but easy to change. I’m suspicious of some of the new wire sets available. Have you looked at the motor running in a low light situation to see if any arcing is going on?

[Darryl D.]

Re: 1966 L79 Wild Bucking

You may want to add some "Heat" to your gas tank, sounds like it could be water in your gas.

[Marc K.]

Re: 1966 L79 Wild Bucking

I appreciate all of the feedback. I started trying easy things first like changing the coil wire. I recalled having bad gas back in the 80's that had similar symptoms and I was considering draining the tank again. I then read a CC Tech article and found the following, "A loose or bad condenser can make your car almost impossible to drive, the engine will buck like a wild horse or make your engine start and stop without warning."

Last time I drove my car, it bucked like a wild horse.

A couple of days ago when I checked the cap and rotor, I made sure the condenser was tight. Today, I removed the cheap Chinese ignition condenser and replaced it with an old AC Delco one that I had sitting around. That did the trick! Unfortunately, I couldn't drive it as it is raining in Seattle.

[Rich G.]

Re: 1966 L79 Wild Bucking

Good news. Thanks for letting us know. Hope it stops raining soon!

Rich