What can cause an engine to (exhaust) smoke when engine breaking but go away during normal driving/ acceleration? I wasn't sure where to post this so if need be move it. It's my wires little gas sipper. I put new rings in the motor but when she down shifts or just let's off the gas for a few moments it smokes. But once she takes off again it slowly goes away until it's not there at all.

 

I would imagine that it is oil being sucked into the cylinders, as when the motor is still turning at a decent clip and the throttle is closed, the vacuum goes way up and can possibly suck in oil past the rings, worn valve-guides/seals, pcv and so on. The issue now would be finding out where it’s coming from.

 

Id have to guess the valve seals.. Like 1bear said, there is alot of vacuum when your engine breaking.

 

I agree......I would say if the rings are new start looking into some new valve seals. Does it smoke a little on a cold startup?

 

I'll have to look next time she starts it. I put a gasket kit in it but not valve seals. It was bit of a generic kit too. Just to get it going so I can build the new motor with turbo later on. I wonder if the Pcv is bad in it. I replaced mine but not hers. Being that I didn't see any smoke at high rpm like it did before I assume the rings sealed good. I did a good hard break in on the rings after I finally got it all together. Never thought of valve seals and it's a high mileage motor.