Mechanics

ACCELERATION SHUDDER

1974 Dodge Dart

Shakes or Wobbles problem
1974 Dodge Dart V8 Two Wheel Drive Automatic unknwn miles

This began 2 weeks days ago. At first. I noticed a slight and almost loop like " dip" in the idle at a stop light. A while later (a week) after a 55 mile hwy drive and arriving at my destination, I was cruising 30mph and then parking lot speeds. When the idle became slightly rough and mimicked a foul plug. I parked and when I returned to head home the problem was gone. A little while (a few days) later. At an idle at a stop light, the " looped dip" in the idle became more pronounce and frequent.. Finally 2 days ago, at a stop light, mind you at warm operating temp, the idle became steadily rough. Upon acceleration, there is a shudder much like a fouled plug. ( Plugs replaced since then). Now, interestingly. Upon acceleration, if I let off the gas for a second and " punch" it a little to get out of 2nd into 3rd. The shutter is gone, it seems..I even noticed some smoothing in the idle when I pulled the manual choke open a bit at a stop. But I won't run like that, of course. Once she smooths out and we slow to another light, you can hear the familiar mopar tranny wind down as normal, all is smooth. And then the shudder begins. BUT if I come to a hard fast stop. Then sometimes the shudder doesn't occur at all. And then upon acceleration its there again. So, should I suspect a fuel/air issue or (gulp) a tranny issue?
So, a little update. I have noticed that coming to a stop fairly slowly and accelerating slowly will bypass this shudder or rough idle. Another interesting thing is. At a stop if I lightly press the brake and allow the car to " push" forward against the brake. If that makes sense. Will take the shudder away as well. Thoughts?
Avatar
74dart
February 1, 2010.




I'd start by looking at the EGR valve. Symptoms sound typical of a flake of carbon holdng it open. The valve should never be open at idle.

Interesting comment about the manual choke. If you need that, it suggests the automatic choke heater passage is blocked with carbon. That was a common problem years ago and was easy to fix. The EGR system uses the same passage so carbon is a likely suspect.

Caradiodoc

Caradiodoc
Feb 3, 2010.


AD