I've was just driving last week and then my ignition had a spasm and it's been happening repeatedly since. I was just driving and it seems like it works normally when accelerating and idling but when driving at a steady speed in the 1200-2200rpm range (cruising speed), the ignition goes haywire. I feels like it just consistently stops firing the same cylinder and it just shakes a little bit and I can feel the loss of some power. They way I know it has something to do with the ignition is because my tachometer runs off of the coil and when it starts doing this, my tach drops 1/6 or the rpm it's actually going. Technically since the car is still engaged and going the same speed, the engine is still spinning the same rpm but the tach isn't getting the correct amount of firing signals so it reads lower than it actually is. I've already unplugged and replugged all of the wires on both ends and taken off the dist. cap to make sure everything is connected correctly. Any ideas?

Try disconnecting your tach for a while to see if your ignition will still 'spasm' without it.
On one very hot Sat. back in 1969, I watched a guy next to me in the pits put several sets of new spark plugs into his sputtering new GTO before this old guy walked up and plucked out his tach lead fixing the problem without even breaking a sweat!

I tried that bu it didn't seem to help.

Then I got my dads opinion and he suggested something I had been thinking about doing anyway. Using a timing light on each wire to see if it was firing. Wouldn't you know it? Cylinders 2 and 6 were causing the sputtering. I'll get a new set of spark plugs soon and report back

If I understand correct. The tach reads the pulses at the coil. This is BEFORE the sparkplug wires.

I would look at the points/ condensor. Tom

Well the tach reads the discharges and if the spark plug doesn't fire, it doesn't discharge and it reads lower than it's actually spinning. Like I said, 2 and 6 aren't firing sometimes and that would cause it to not discharge and not read correctly. So new spark plugs should fix it. Have you guys heard good things about e3 spark plugs?

The tach reads the closing of the points. When the points close, The terminal is grounded, this is what the tack reads. This is also on the primary side of coil. The sparkplugs are fed by the coils secondary side.

Hope the plug wires fix it. If I remember correct, you changed them not that long ago when you were messing with the carb and ignition.

I use standard AC plugs. You really need to change over to a HEI. The engine will run better. Tom

Nope. I replaced the points, condenser, rotor, and cap. I tested all of the wires for resistance and they were all fine. funny how the only thing I didn't test or replace was the spark plugs and they seem to be the thing that's failing.

Believe me, I want hei. Hei and an msd ignition are in my future after I yet the turbo on

It seems odd that two plugs would be misfiring at the same time and they began doing it at approx the same time.

Have you checked the primay and secondary side of the coil? If I were guessing I would swap 4 plugs around into 2 & 6 and see if the problem persists at those same cylinders.

Do the pickups on the cap at 2&6 look similar to 1,3,4 & 5? Don't be surprised if your new cap is defective.

X2 on the HEI ($26 from my local U-Pull-It)

Good luck

>>Cylinders 2 and 6 were causing the sputtering.<<
And you also said
>>works normally when accelerating and idling<<

If it was missfiring at idle, you would feel it and hear it.

It is not uncommon for some timing lights to act that way. Move the plug wires around and/or pick a different location for the pickup.

It sounds like you replaced the points not that long ago. The rubbing block under the point arm will wear more the first few hundred miles than it will in many thousands of miles after that. If you set the points on the close side and the block wears down, decreasing the gap, the dwell can increase above the correct setting.
At cruise the vacuum is the highest and the vacuum advance is pulling the breaker plate the farthest. You should check the breaker plate pivot pin for wear. The breaker plate on the 250 I6 is not the best design and dwell can change a little when the engine is reved and when vacuum advance is added.

Do you have a dwell meter?

My guess is that if you didn't notice the problem between last week and when the points were new (recent past?), then you need to reset the dwell and timing.

I do have a dwell meter and I replaced the cap, rotor, points, and condenser in June. Just checked it this morning and it was 36 or 37 degrees instead of the 32.5 degrees it was supposed to be. I set it to 28 just to be sure that it was causing it. I already ordered new spark plugs so if this fixes it then the old plugs were something I needed to replace eventually anyway. I'll check the timing after school.

Well it didn't fix everything but it fixed the spasms. I still have random misfirings to where I'm just driving along and one of the cylinders don't fire and it shakes the car a little and decelerates for a split second. I hope the new plugs will take care of that. I get them on friday so I'll let you know

Alrighty guys. Put in the new spark plugs. Fixed the random misfirings. Everything is smooth as butter :-))))

The only thing that bugs me now is the hesitation when I floor it at low rpms. If I'm cruising at like 1500rpm or something and I floor it, It just acts like it dies for half a second and then it sputters back to life and then accelerates normally. Is this from too much gas out of the accelerator pump and it can't handle that much richness at low of an rpm?