Kingtal0n

In Closed loop at idle the engine runs fine, but has a rich smell. The Plugs, however, Are pretty clean and white. My O2's in Closed loop are flipping Normally, perfectly. It does not seem to miss.


Im wondering if maybe the location of the O2 sensor (end of longtube Header) is causing a slightly skewed O2 voltage which is keeping the A/F slightly richer or leaner than ideal, which is causing the slight rich smell im getting. but why are the plugs white and clean if its running rich?

Maybe its a lean miss which causes a lean O2 voltage but a fuel smell when the unburnt fuel hits the exhaust?

The cam is not tiny either, would it be the less efficient burn during idle causing it?

Just trying to figure out why its running good but smells like its running rich.

Damon

As long as the O2 is before the cat and you don't have any exhaust leaks it'll work. How close it is to the engine can affect how long it takes to reach operating temp but it won't affect the readings.

I have talked to lots of guys using O2s with big cams- they usually have problems in CLOSED loop at idle. The large cam's "overlap" throws lots of unburnt fuel and unburnt oxygen into the exhaust and makes the O2 sensor's readings at idle less than reliable. I'm told they either shoot for a slightly richer idle mix (numerically lower than 14.7:1) or just ignore the O2 readings at idle in the programming.

In OPEN loop- when the compuer's just reading the fuel map and spraying the fuel in they seem to run OK, assuming the programming is reasonably close.

If you have a big cam it's GOING TO give you that "unburnt fuel" smell out the pipes at idle, even if it's tuned reasonably well. That's just how big cams are. If you don't have a cat then it's almost guaranteed.