I havn't changed my o2 sensor yet due to some advice that the plugs were causing my car to hesitate as if she wasn't getting gas every now and then when cruising along. So anyway I threw in some new plugs, oh by the way...the old plugs are all pretty much jet black, anyway I put the new plugs in and she ran great for a whole 2 days. Now its starting to feel like there are imaginary bumps along the road again. What could be causing my plugs to keep fouling? o2 sensor? I havn't used the nitrous in some time either.

When an O2 sensor goes bad it will normaly, although not always, cause the car to run rich.

This could be what is fouling your plugs if the bad O2 sensor is making the car run extra rich.

Thats what I was thinking. But I was still expecting my Check Engine light to come on if the sensor ever went bad.

I think that the O2 sensor can still be a little off without the tripping the light. That might be your problem.

When you can't figure out exactly what is causing a problem going through all the possibilities starting with the cheapest first is usually the best bet.

The O2 sensor is probably the cheapest part in the list.

Well.. I don't know if this is true or not.. nor did I get a response on this board when I posted a ways back... but according to a few speed demons ( from last summers street race meets ) NOS will eat your cat coverter cause there'* always excess fuel that gets to the cat when on WOT and gets burned in the CAT, but NOS that gets there will burn hotter and thus causing the Cat to burn out quicker.. whether this maybe your problem or not I don't know. Whether this is true or not.. I dont' know.. I only have 3 people tell me this.. and they all know of each other... any input on this? :?

Believe me, its not a CAT problem. heheh

When you say your plugs are black.... are they dry, sooty black, or are they sticky, crusty black, with a pronounced "greasy burnt hamburger" look? How many miles on them? When was the last time you saw your plugs nice and tan or white? What mods have to done since? How many miles since?

If dry, sooty could be rich. If Sticky, crusty black, could be oil consumption caused by:

1. Intake manifold seal leak (PCV to manifold leaking oil).
2. Worn valve seals.
3. Scuffed cyl walls, pistons, etc.

Definatly dry. You can takes off most of it with your fingers.

I narrowed it down to my o2 sensor or my MAF sensor.

Dry? Sounds like carbon. Unburnt fuel leftovers. I'd bet you're running rich. Anybody know of any ill effects NOS has on an O2? I know a coolant leak into the cylinders will kill an O2 in short order.

NOS itselfs damages an o2 sensor quicker from what I know. After I get some cash this week I'll buy a new o2 sensor and see what changes.