PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

weird wideband readings

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Old Oct 21, 2009 | 10:31 AM
  #1  
streetassasin's Avatar
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From: Orange, TX
Default weird wideband readings

The car was tuned before I got it but Ive made a few changes since then
Changes:
SLP maf to a stock maf
added ftra
tci 3500 stall to circle d 3800
stock tb to ported tb
high flow fuel rails
2.5" Y pipe with a spiral flow to a 3" Y with dual cutouts and a dynomax bullet
msd wires
tr6's to br7ef's
walbro 255
After the exhuast went on the car ran horrible and would pop through the exhaust at anything over 2500 rpm and shake the car, The next day I changed the plugs and wires, they were gapped between .015-.040 . I gapped the br7's all at .030 and it made the shake go away but it still poped through the exhaust so I figured it might be going lean so I hooked up a fuel press. guse to the rails and it was showing 58-60psi steadily. Finally yeterday I hooked up my LC1 that I had on my old ss. I made sure all the grounds are good and grounded the blue wire to the driver side head. The guage reads around 19-20 to 1 most of the time but will dip down to 9.5-10 to 1 sometimes and jump right back up to 19. Could it be reading right and my car has that bad of a tune on it or is something wrong with the wideband?
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Old Oct 21, 2009 | 10:46 AM
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Sounds like what happens when a (Bosch LSU) sensor is on it's way out...
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Old Oct 21, 2009 | 10:57 AM
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Brand new o2

This is the one I bought, http://www.jegs.com/i/Innovate+Motor.../3737/10002/-1
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Old Oct 21, 2009 | 11:52 AM
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leaks in the intake, leaks in the exhaust, and misfires can cause what you are seeing as well. FYI, in the future, this will save you almost half of what you paid for that sensor: http://www.oxygensensor.net/widebandsensors.html
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Old Oct 21, 2009 | 01:14 PM
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thanks for the link, wish I knew about it before I got this one from Jegs. The car did recently throw a ses light so Ill have my buddy scan it today or tomorrow to see if its a misfire. The only place the exhaust could leak it at the header flange, headers are welded to the Y, I checked the bolts and they seem tight. Would it be worth it to change out the header gasket? to see if that fixes it. And is there any chance that its reading right and my tune is just that off?
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Old Oct 21, 2009 | 01:30 PM
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Did you do the free air cal? I obviously wouldn't think that reading is even close, so long as the car is still using closed loop it should bouce around 14-15 unless WOT. See what code it's throwing.
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