How can you tell if you need to replace your motor mounts? I have the classic cracked exhaust manifold and know this can be caused by bad motor mounts. I am about to fix the manifold with an APN. I have visually inspected (what little I Can see looks good).

I have a slight "rough" idle and will be changing fuel injectors and a new O2 sensor as well. When in park and at high revs the motor does not seem to shift or shake a lot.

Just wondering if there is any way to tell if the mounts are bad before I should bear the extra cost of replacing the motor mounts and renting an engine hoist to replace the mounts.

 

Try prying on one side of the mount with a pry bar.

If it moves more than a little they are bad.

 

^^ You can do it that way or you can have someone watch the engine, start it up, put it in drive and give it some gas. You will see the engine shift if the mount is bad. You can also check the other side by doing the same but putting it the trans in reverse.

 

Be careful as a worn trans mount will cause rotation if checking that way.

Both should be replaced at the same time, tho.