Why does my engine idle rough but the car isnt missing?

[john rutenberg]

My 79 Seville is finally all complete with the repairing of all the emissions systems, wires, plugs, computer, distributor EES modlule. The car passes smog like the car isn't running. The exhaust at the pipe doesn't have a single sputter, yet the car idle is rough. Any ideas? I am wondering if the motor mounts are dry ( not broken, but dried out0 letting vibration into the body. Thoughts?

[John Morris #23947]

The most likely thing would be a vacuum leak. Especially with newer cars, they have sooo many vacuul lines and fittings, which were apparently all just pulled and replaced.

[john rutenberg]

No, like I said the car runs well there are no leaks but the car shakes. The exhaust is clean smelling and it come out streaming without a sputter. Im wondering if the mounts need replacing. Maybe the motor and the trans mount.

[The Tassie Devil(le)]

G'day John,

Bad engine mounts will cause what you are describing.

I don't run any insulated engine mounts on my Dragster, and even with a wild cam, the engine still runs sweetly, fastened to the Chassis Rails.   And I am running simply Hose Clamps to keep 750 HP in place.

The '89 T'bird that I travelled 14,500 miles around USA and Canada in '02 had two broken mounts, and that thing ran sweetly, all the way.   The Engine couldn't fall out as the engine mounts were the "Safety" type, so it wasn't a major problem.

Bruce.  

[Wayne Giguere]

My 79 Seville is finally all complete with the repairing of all the emissions systems, wires, plugs, computer, distributor EES modlule. The car passes smog like the car isn't running. The exhaust at the pipe doesn't have a single sputter, yet the car idle is rough. Any ideas? I am wondering if the motor mounts are dry ( not broken, but dried out0 letting vibration into the body. Thoughts?

We had the same thing on a 71 with only 29000 miles on it. Tried everything and finally did a valve job. No more problems.