Why would this tuner used at the low setting cause an 02 PSD to blow black exhaust on acceleration? And it's only when really standing on it from low speed or if it down shifts while already at highway speed. Is it over fueling? I don't have to breath it, but can it cause problems? The truck has an oversized exhaust system. Thanx.

 

black smoke = more fuel and it shouldn't hurt a thing mine does it on my 2000 but I don't get on it very much.

refuse2

 

I don't run my truck hard at all. It just happened that one time when I did, the sun was comming up behind me and I saw it in my passenger mirror. So of course, I've done it a couple of times from different speeds and here we are.

 

A lot of times if you don't goose the throttle a lot there will be a buildup of carbon on the inside of the exhaust system. Even NA engines will do this. The next time you floor it the blast will clear out the carbon from the inside and make it look like the engine is smoking. If you see that big puff and then duplicate the conditions right away that produces the puff and see a lot less or nothing, that is what it is.
In fact here in Washington when you go into the emissions test station to get your diesel smog tested, one of the things that they have you do is to snap the throttle wide open three times just to clear out the carbon. Without doing that it makes the puff of smoke big enough to give you a failed reading.

 

The sun coming up behnd you made it look worse than it probably actually was. You'll notice the exact same effect at night when there are headlights behind you.