Black smoke/soot out of exhaust

[turbospyder19]

For awhile now my car has been running rich, but I figured it was a normal side effect of 15 psi on stock everything. Recently, however, my problem has gotten worse. Now that cold weather is coming in, I can see a black/grey cloud in my mirror when accelerating onto the highway to go to work (before the car completely warms up) and friends have told me that it smells like sh*t behind the car. There is also black soot speckled on my bumper and caked in the muffler tip. The problem gets noticeably better once the car reaches operating temp., but never completely disappears. Sometimes the power will disappear like I'm braking, but I'm still accelerating (don't know if this is related) and it feels like my power is gone till I let off the throttle and try again. This also gets beter when warmed up. I've tried a boost leak test, but found nothing. Would a boost leak improve once the engine warmed up? Or do I need to invest in a logger/safc? Sorry for the lengthy post, but thanks for any help!

 

[I-luv-em-all]

could be a bad O2 senser, and the cold weather brings out the worst in a car and just plain doesnt help anything.

 

[Meh987]

could be a bad O2 senser, and the cold weather brings out the worst in a car and just plain doesnt help anything.

I agree that it could be a bad O2 sensor. Are you getting bad gas mileage?

 

[blackGSX2g]

A logger is never a bad thing to invest in. It will tell you if you need a new o2 as well as aid you with any future tuning. Your situation meets most of the symptoms for o2 failure. If you don't want to get a logger or can't afford one, just measure your o2 volts from the o2 wire leading to your ECU. Hook it up to a voltmeter and drive around. A normal o2 sensor will jump around and start to stay around .9x at WOT in the upper rpms. A dead o2 sensor, however, will display very low voltage, showing your ECU that there is a dangerously lean condition. The ECU then goes into 'dump fuel' mode.

I don't remember the color of the wire that goes to the ECU, but I'm sure someone on here does. I'tll prolly show up in a search of an A/F gauge install.

 

[turbospyder19]

At first I thought it was a bad O2 sensor so I scanned it at school. The sensor went rich, lean, rich, lean, rich, lean like it should, so I'm pretty sure that's not it...my gas mileage is about 20mpg, is that normal? Would an S-AFC be the fix for this problem?

 

[blackGSX2g]

Well, with the o2 gone on my GSX I got about 16-17mpg. When I got the logger and MAFT, I brought it up to about 24. I would assume yours should be a bit higher than that. If you get an AFC, make sure to get a logger for it though. Have you tested for a leak when its cold?

 

[turbospyder19]

Working on re-testing the boost leaks...

 

[leet]

Don't forget that condensation will do the same thing.

My car does that whenever it gets cold.