my car knocks ,vibrates,and rocks side to side.?

Question

what causes my 1991 caprice classic to knock and vibrate when i start it after it sits overnight? after it warms up it runs find all day.until it sits overnight again then it knocks. rocks, and vibrate all over again.

Answer 1

i own a repair shop,and it sort of sounds like you may have a bad set of lifters in it,that will cause one to do this real bad,and also having the wrong weight of oil in it will cause this a little also,what i would do if i was you id take it by a local shop,an ask for a hands on opinion on it,this way you can sort of get different views on it,also the timing chain and gears will cause one to do this real bad ,when they get worn down,gm uses a soft metal to make the gears with and it doesn't last all that long sometimes and this throws the timing real far off,and changing it at the distributor doesn't help it,because it still doesn't fix the off set of the valves opening at the right time,the only true way is to replace the chain and gears in it,and believe me you,ll think you got a new engine in it,it will run and perform really well,its something to check though,i do about 35 - 40 gm product a year just on timing chains and gears alone,and it helps every single one of them i do,good luck i hope this help,s.

Answer 2

Sounds like a blown head gasket. Do you have to top off the radiator?
May sound weird but try this...
Loosen the radiator cap. Winter time, you don't have to worry about overheating.
If your problem goes away, it's the head gasket.
Reasoning: Pressure builds in cooling system when it's hot. When you park it over night, that pressure "releases" thru a hole in the head gasket that puts water into one cylinder. When water is in a cylinder, it won't fire properly and cause a knock and rock.

Answer 3

It is not running on all the cylinders while cold. From my arm chair 2000 miles away it looks like it could be a number of things including bad plug wires, overly lean start up, etc. Time to have a mechanic check it out when cold.

Answer 4

You need to consider replacing the cap, rotor, wires, plugs, and coil wire. Your wires appear to be breaking down. While doing this make sure that the coil wire post is clean from any corrosion.

Answer 5

Have your ignition tune up items checked (plugs, plug wires, distributor cap and rotor etc.)

Answer 6

That's funny my ole lady acts the same. And I found her at a used car lot.

Answer 7

it`s time for a new ride, my friend..1991??

Answer 8

a girl in the back seat???