well i'm running a 408(specs in my sig). right now it has about 500 miles on it. i was on the highway the other day in 5th gear and i stepped on the gas pretty hard to get the car going faster. when i did this the the motor started to studder. i feel it thought the stick and the gas pedal as well as the car jerking a little. the car runs fine. it only does it when the car is in a high gear at low rpm and you step on the gas hard. i replaced the fuel filter and that didn't change anything. any suggestions as to what this could be?

i think it might be:
-a timing problem
-something wrong with the carb
-something wrong with the coil (i still use the original distributer and i have new plugs and wires)

 

An engine that hasn't sealed yey, and is under steady load may not be getting even compression.

For insurance, you could pull the plugs and take a peek at their condition, which should be a good indicator of fuel mixture. Disregard any oil you may see on the plugs, since you're breaking in the rings.

Beyond that, I wouldn't be too concerned unless the problem gets worse or doesn't go away after another 500-1,000 miles.

 

it never did this before. is this unusual. is there any way help it get better.

 

I would check all your ignition parts. My car did this when it had a weak spark. I think your on the right track when you say it may have something to do with the coil. Make sure to look at the cap and button. Sometimes the the carbon brush gets too hot and burns the cap and button.