black smoke at revs - o2 sensor to blame?

[aesc]

I thought i had this figured out but due to another earlier post now i have my doubts.

My Levin seems to spit out black smoke when I thrash it. Its kinda random though, because sometimes you can see lots out the back but other times cant see anything. I was thinking that its possibly the heater on the sensor. The reason I think this is because is spits out black when the sensor may have had a chance to cool down (heater not working) like after ive been idling sitting at the lights or cruising along at low revs. I know there are other reasons why it may be doing it, but is it most likely to be this? Does anyone have any previous experience with black smoke problems and fixing it? Also, could this be the reason why my engine oil gets black so quick? Too much fuel (rich A/F) as determined by the o2?

Also Ive read a few technical articles, and under WOT, the fuel management system is in open loop mode, so the amount of fuel being entered into the engine isnt determined by the o2 sensor, the computer uses info from other sensors. In closed loop, such as idling or crusing, the o2 sensor is used for A/F ratio. Is this true?

I have tested the heater coil on my sensor with a voltmeter. Apparently, if it reads between 3.5-4.7 ohms its sweet, but mine measured 6.3 ohms with about 10 mins cool down (after i turned the car off). Does anyone know if resistance changes with heat i.e resistance is not constant?

Any help or insight would be appreciated.

[KinLoud]

The 4agze with factory computer goes quite rich with full boost - hence the black smoke. Don't stress about this just about every GTZ I've seen does this.
It goes rich on boost to make very sure there is no detonation - a typical factory thing with boosted cars to make sure they have a long life.

Ken
Taupo
021 408 863

[Wildcard]

I have tested the heater coil on my sensor with a voltmeter. Apparently, if it reads between 3.5-4.7 ohms its sweet, but mine measured 6.3 ohms with about 10 mins cool down (after i turned the car off). Does anyone know if resistance changes with heat i.e resistance is not constant?

Yes it does, they can read quite wildly differently when not up to temp....

As Kinloud says, doesn't sound like anything to worry about

[aesc]

Cheers people, I wont worry bout it anymore!

If i put a bigger pulley on it, would it run even richer (and be more black smoke) or would it not change?

[Wildcard]

Cheers people, I wont worry bout it anymore!

If i put a bigger pulley on it, would it run even richer (and be more black smoke) or would it not change?

Depends on how your ecu is mapped. I would assume a similar or greater level of smoke [unburnt fuel]. The ECU is dumping this amount of fuel to keep temperatures down and therefore try to avoid detonation, as boost levels rise so does the chance of detonation....