Leaning out

[90AWDGSX]

My 96' GSX with a 14B and 450cc injectors is leaning out once it warms up. When it first starts up it runs 2 bars into rich on my A/F gauge at full throttle to about 5200 rpms. But once it warms up it drops off the gauge on the lean side. What could cause this? 02 sensor or cracked injector. Help please before my new bottom end kicks the bucket!!!

[phastalon]

I had that problem for awhile, and since I was poor i just turned the boost down. Later I figured out my O2 sensor was on its way out. I replaced it and everything was fine. I have heard alot of people say that when you hook up the gauge its best to replace the sensor to. I dont know if theres alot of truth to that but I would start there.

[90AWDGSX]

Cool thanks for the info. My 02 sensor has been through a T-25 and two 14B's so its probably about that time.

[Mirage]

Get a logger and a fuel pressure gauge. If your fuel pressure is dropping under load, then it'll go lean as you described. This can easily blow the new bottom end. If the fuel pressure isn't dropping, then I would log it to find out what the fuel trims are like along with if you're maxing the injectors, maxing the MAF, etc.

When the O2 sensor warms up, it's normal for it to drop in voltage, but not that much. I've seen changes as much as .05 volts, but never more than that. On the blinky light gauge, that would probably be about one bar leaner.

One other thing, get rid of the blinky light A/F gauge and get a gauge that you can actually use. These don't have the resolution nor the accuracy (with a stock O2 sensor) to be of any use for tuning. About the only thing these are good for is to make sure that your o2 sensor is still working.

Try this and report back the results.

[v413nc3]

If you *MUST* use a narrow band O2 sensor then get a jumptronix. Those blinkie light things are for honda guys and idiots who need an extra gauge (no offense to Patrick who was filling a hole).

[90AWDGSX]

Where can I find a decent way of mapping the A/F ratio that won't kill my pocket? And what kind of 02 sensor should I get that will be useful in future tuning? I hear all this wide band narrow band talk and its all japanese to me. What is the difference?