Still Jerkiness during Cruise

[Red66GT]

The car idles fine, and is smooth during acceleration and deceleration, but for some reason when I am just cruising the car feels jerky.

I checked the motor mounts and they are fine, I can also pretty much rule out the possibility that it is a carb problem, b/c I just switched back to my Edelbrock 600cfm from my Holley 600cfm.

Can it be something wrong w/ the ignition system such as the coil, plugs, plug wires, etc... (Note: I use the pertronix electric ignition so it's not a points problem)

Can it be a fuel pump problem??? Any suggestions

 

[Pakrat]

Have you checked your fuel filter lately? Maybe the passage is partially clogged which is why you don't notice it under load but when cruising you are starving it slightly.

 

[69 Capecod]

Hey pak
Hows the car.

Sorry for the high jack.

 

[yeloxr7]

If you are powering the Pertronix off the coil + wire (resistance wire), you may be having problems due to the voltage drop (the voltage at the coil can drop to 6 - 7 volts). I had similar problems until I changed to switched 12 volt power to the ignition module.

 

[Red66GT]

I just changed the fuel filter last week so that is not the problem.

"If you are powering the Pertronix off the coil + wire (resistance wire), you may be having problems due to the voltage drop (the voltage at the coil can drop to 6 - 7 volts). I had similar problems until I changed to switched 12 volt power to the ignition module. "

How did you do this exactly? and what do I need to buy?

 

[TT670]

It sounds as if its lean

 

[mikec35]

If only under a load I would be very suspicious of either a bad plug or wire. How old are the plugs and wires? Easy check is to run the engine in complete darkness and have someone rev the engine while the brakes are applied.. you will see the spark plug wires arc if they are bad. I also would be suspicious of your torque converter. Has the transmission fluid been changed lately? Make sure you don't get your foot run over while checking the plug wires!! good luck...

 

[Red66GT]

I'd say the plugs are less than a year old and the wires 18 months.

The tranny was filled w/ new fluid about a year ago, so should be fine, it's a 4 speed manual T-10 Borg Warner.

As far as the problem occurring when the car is under a load I'm pretty sure this is Not the case, b/c when I accelerate fast its fine, and it also seems to be fine when I'm going up a hill.

The problem is just when the car is cruising at a steady RPM.

 

[latamud]

I had the same problem a few years ago. It was jerky driving through a parking lot at low speeds in firsrt and second. At the time it felt like the rear end was jolting. I installed Shelby underides and it did help but wasn't the fix. I had new motor mounts but new doesn't mean good. I installed a turnbuckle from the frame to the block and tightened it down as far as I could get it. That sold the problem. It did come back after a year but it was that the turnbuckle backed off a little, so I put a nut to lock the one side down. The other side is a left hand thread. Maybe that'll help you. Good luck.