When Boost Rises, 02 Readings Fall.

Brent · 02-17-2008, 07:04 PM

Given your narrowband O2 Sensor is by no means the most accurate, .02 means you are running very lean. On a stock O2 Sensor if I remember correctly, the "ideal" voltage is .45... which means it is at an optimal air/fuel mixture. Anything below that is lean, anything above that is rich... relatively... based on the number. I'm sure you already know that, I just wanted to throw that in there for anyone in the future that may experience the same problem as you that is searching.

Does it always lean out at 4000rpm's or only when under heavy acceleration?

***ZGN*** · 02-17-2008, 07:12 PM

It only runs lean when under boost, I can gradually accelerate the car to 6000+ and it reads .84 to .89

***Herblenny*** · 02-18-2008, 01:23 PM

I agree with Brent... narrow band is useless.

First of all, Check your ground. Make sure the ground to your engine is good.

If your car was running fine before, it shouldn't be anything to do with the tune.

Also, since you are non-seq, there shouldn't be much troubleshooting regarding vac lines.. Check those just incase..

***ZGN*** · 02-18-2008, 02:43 PM

Checked for vacuum leaks and found none. I pressurized the intake with 5psi useing my air compressor.
I bet it is related to my leading coil pack or msd6a
or it could be a drop in fuel pressure but i don't know because my gauge is under the hood, Hard to read while driving.

***ZGN*** · 02-21-2008, 10:24 AM

Quote:

Originally Posted by RotaryResurrection

Even though it seems ass backwards in my mind, a bad coil or a fouled sparkplug that is not firing on one chamber, will cause an o2 sensor to read lean. I would expect it to read rich, due to all the unburned fuel coming through the exhaust from the non-firing chamber. But I have seen it a few times on my own car with a wideband when i was running 10.5 race plugs that foul at idle easily.

That said, i wouldnt rely on that stock sensor for jack shit. You can get a wideband with display for as little as $250 these days. Hell, if for no other reason, it will teach you to drive the car more efficiently for MPG when you're not on the throttle. You'll find out a couple of surprising things about when your engine is most efficient.

That is what I am suspecting also, I cleaned the plugs. but still same results.
I am useing a 2nd gen leading coil pack with a MSD6A. This weekend I'll desolder it all and reconnect it to reassure me it's not a loose wire. how do I verify the MSD6A is working properly? Or maybe my leading coil pack is going out again. I had previously blown a stock leading coil pack with this setup. It literary blew it apart.

02-17-2008, 07:04 PM	#1
Brent Sua Sponte Join Date: Feb 2008 Location: Killeen, TX Posts: 839 Rep Power: 18	Given your narrowband O2 Sensor is by no means the most accurate, .02 means you are running very lean. On a stock O2 Sensor if I remember correctly, the "ideal" voltage is .45... which means it is at an optimal air/fuel mixture. Anything below that is lean, anything above that is rich... relatively... based on the number. I'm sure you already know that, I just wanted to throw that in there for anyone in the future that may experience the same problem as you that is searching. Does it always lean out at 4000rpm's or only when under heavy acceleration? __________________ Road Atlanta August 2011 NASA TT 1:33 http://www.youtube.com/watch?v=IFY00PAK_Ps Traqmate's video of my car from the 2011 UTCC at VIR http://www.youtube.com/watch?v=2Zcn6...layer_embedded Video of Yellow LS1 FD at NASA TT at VIR http://www.youtube.com/watch?v=e6k0lJkcwrM

02-18-2008, 01:23 PM	#3
*Herblenny* Founder/Administrator/Internet Pitbull :) Join Date: Jan 2008 Posts: 644 Rep Power: 10	I agree with Brent... narrow band is useless. First of all, Check your ground. Make sure the ground to your engine is good. If your car was running fine before, it shouldn't be anything to do with the tune. Also, since you are non-seq, there shouldn't be much troubleshooting regarding vac lines.. Check those just incase.. __________________ DGRR 2013 - Year of 13B www.DealsGapRotaryRally.com http://www.facebook.com/Herblenny

02-17-2008, 07:12 PM	#2
*ZGN* Administrator Join Date: Jan 2008 Location: Birmingham, AL Posts: 2,264 Rep Power: 10	It only runs lean when under boost, I can gradually accelerate the car to 6000+ and it reads .84 to .89

02-18-2008, 02:43 PM	#4
*ZGN* Administrator Join Date: Jan 2008 Location: Birmingham, AL Posts: 2,264 Rep Power: 10	Checked for vacuum leaks and found none. I pressurized the intake with 5psi useing my air compressor. I bet it is related to my leading coil pack or msd6a or it could be a drop in fuel pressure but i don't know because my gauge is under the hood, Hard to read while driving.