by cammerjeff » Wed Jul 15, 2015 8:13 pm
Is it a 2.5 Iron Duke, or a V-6? Either way I would check the condition of the Motor Mounts and trans mount 1st. A bad trans mound can cause a lot of shaking side to side at idle. If it is a Buick V-6 even the 77 and later even fires do not idle very smoothly, not like a modern V-6. But other than mounts, an ignition problem can cause it to shake, to low an idle speed can do the same thing. I have found the Buick 3.8 in my 78 Sunbird likes to idle at around 850 RPM a couple of hundred higher than the factory specs. at 600 it tends to shake a lot more.
What I found on my Sunbird causing it to shake very badly at idle, and have almost no acceleration was the Torque converter was actually bad, it was stuck and not doing any torque multiplication. But that is a very rare issue, usually found on a car that sat for many years. And that described my car before I bought it.
Give us alittle more info, besides engine type and size, Auto or manual? If an auto does putting it park or neutral affect the shaking? Compared to idling in gear. What is the Idle speed? More info never hurts.
Jeff R
1971 Catalina Freeway Enforcer
77 Astre Formula, some day soon powered by a 215 Buick V-8
1973 4-speed Lemans Safari STOCK!!!!! 1978 Catalina Safari
2006 Mallet Solstice, 6.0 LS2, 6-speed manual
2009 Solstice Coupe, 2.4, 5-speed Manual