Shuddering and lunging

[jaybee47]

Shudders when low pedal is depressed when starting out at proper spark and throttle lever positions.
Lunges and wavers at high gear, smooths out only at full throttle at proper spark lever position. Full throttle too fast and risky for certain road conditions.
What are the causes?

[Norman Kling]

Sounds like a problem caused at high compression. Quite often this problem is caused by a bad spark plug, or a coil out of adjustment. If the spark is weak, it will not jump the gap under high compression. You might try cleaning the plugs or replacing them and setting the gap about 25 thousandths. However it could also be caused by carburetor problems at low speed. It could possibly be starved for gas at low speeds or even running too rich at low speeds. Check your float level, and the adjustment of the mixture.
Something far off and not expected happened with a friend's car. It was running rough at low speeds and we thought it was an ignition problem or carburetor problem, however he had non demountable wheels. The rivets holding the felloe to the rim were broken and the rim was offset from the felloe. At low speeds, the wobble was noticeable, but smoothed out when going faster. It actually felt like a misfire, however, it was not. He sent the wheels out to be re-spoked and the problem was solved.
Norm

[Scott_Conger]

To even hazard a guess would require more answers to more questions than I'm willing to type.

You've given symptoms, but zero background. Fill in lots of missing pieces and then get lots of opinions, nearly all of which will invariably be wrong, since they will be guesses without seeing or hearing the car. You would be a lucky man to find someone who diagnoses your problem, and if someone does, how will you know which one was correct? This is how to be sure to end up disassembling the car starting at the wrong end.

To recap: fill in lots of missing pieces to your story and you'll get your solution