Slight miss at idle

[Vanspeed]

Hey guys I have been chasing this issue for a bit and nothing I am trying is curing it. At idle it runs fine but every now and then there is a slight miss, sometimes a quick miss, sometimes a bit longer but it never dies.

Take the car out on the road and it runs fine, nice throttle response and no noticeable stumbles or anything. The other day I pulled a plug wire while it was running and noticed that when I heard the stumble, there was also a stop in spark, very briefly. It will do this to what ever plug wire you pull. When it stumbles for a second, there is no spark.

I have tried a new coil, new condenser, and pulled the cap. Looks ok inside. Any ideas? This engine has only been in the car for around 2 years and this slight stumble was not there when I first installed it.

Engine is a ‘36 LB, bubbas distributor with crab cap. Converted to 12 volt. Converted 12 volt generator, 1957 ford voltage regulator (30 amp)

[40cpe]

It has ben noted several times that the ignition switch will sometimes get corroded contacts and make intermittent contact. Something to check. Maybe put a test light on the ignition wire to the coil and watch for skips.

[Vanspeed]

After a stop today with some friends at a horse barn/winery I noticed that when the engine is up to temp I do not notice the miss. Only seems like when it is cold?

[koates]

Vacuum leak on the intake manifold or similar. Use a vacuum gauge to diagnose this problem. Swapping out coils and condensers and fuel pumps etc is just a waste of time. You need to actually test for these problems. Regards, Kevin.

[35fordtn]

Check the spring loaded terminal where the distributor wire attaches. Sometimes the plunger in the terminal seizes up and makes a intermitant misfire.

[Vanspeed]

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Originally Posted by 35fordtn

Check the spring loaded terminal where the distributor wire attaches. Sometimes the plunger in the terminal seizes up and makes a intermitant misfire.

That is a spring loaded terminal where the wire and condenser attach?

[35fordtn]

Yes..

[supereal]

The non metallic spark plug "wires" can cause that problem. as can worn or loose terminals that rely on a "prong" to pierce the insulation. Many of the carbon fiber type were installed to reduce radio static. Usually, new spark plug cables will cure the "skip". At our shop we solder the connectors to the copper conductors to assure connection at all speeds.

[Vanspeed]

Originally Posted by supereal

The non metallic spark plug "wires" can cause that problem. as can worn or loose terminals that rely on a "prong" to pierce the insulation. Many of the carbon fiber type were installed to reduce radio static. Usually, new spark plug cables will cure the "skip". At our shop we solder the connectors to the copper conductors to assure connection at all speeds.

Not sure where I got the wires but they were not cheap if I remember. They are color coded and the end is soldered on that goes in the cap.

[Vanspeed]

Originally Posted by 35fordtn

Yes..

I noticed I loosened that stud while taking off the old condenser so I tightened it back up. It has two square tabs, needed to use a needed nose plier to tighten it back up. I will check that.