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67 289 engine vibration

6925 Views 16 Replies 6 Participants Last post by  Dboxman7
On the freeway most noticeably above 60 mph, when on even flat road if I let off the gas, no problem, but when I give just enough to maintain speed I get a heavy vibration/shaking feel from the engine. Not violent like something is breaking, just too heavy to feel right. Doesn't do it when accelerating or when I let off the gas. I haven't started to try to diagnose yet... maybe vacuum advance? or ignition/timing?

Any thoughts or help appreciated!
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Thanks for the suggestions. The engine is stock, vibrations just became noticeable last week. I have had the car over a year with no problems. Both u-joints are solid and the pcv valve seems fine. Still need to check the torque converter bolts and ignition.
Are the motor mounts in good shape? A loose/worn mount (driver side) would not show up during acceleration.
Yes, as Rex1965 mentioned, the joint cups need to be "relaxed" after the "cir-clip" is installed.
Happy Motoring.....
1 - 3 of 17 Posts
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