LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

running rich

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Old Oct 20, 2010 | 02:40 PM
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wheelliftnpony's Avatar
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running rich

Over the past two years or so I have noticed the car has been running richer and richer. First was gas mileage then a little black smoke so I checked the oil and sure enough it smells like fuel. What can cause this? All the plugs look great and the car runs fine, I'm just worried about washing the rings or wiping out a bearing :s is there anything I can do through the pcm (Delete o2 sensors, etc.) That will help? Thanks, Chris
Old Oct 20, 2010 | 03:30 PM
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Things that cause a "false lean" condition, causing the PCM to add fuel the engine doesn't need:

-misfires
-exhaust leaks before the O2 sensors
-defective O2 sensors/wiring
-high overlap cam
-O2 sensors in open header collectors

Things that dump fuel:

-leaking fuel pressure regulator
-excessive fuel pressure
-leaking injector(s)
-faulty tune

If the plugs don't look bad - e.g. no carbon deposits - its probably not running rich. Are they ALL clean? A leaking FPR for example, dumps fuel in the rear cylinders.
Old Oct 20, 2010 | 04:18 PM
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Funny you would mention a false lean condition. Took it for a drive just a few minutes ago and the ses light came on. I had my tuner from Trifecta with me. So I scanned it right away. Got code 44. Left o2 sensor lean. I'm thinking now it's a faulty sensor, maybe pcm trying to fix a problem that isn't there..
Old Oct 20, 2010 | 05:03 PM
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You would be wise to check the plugs on both banks to confirm what the code reader says. Since you need to replace the dark ones anyway.

But since you've been driving it this way for 2 years, it needs a lot more than just plugs on the left bank and a single O2.

Last edited by Guest47904; Oct 20, 2010 at 05:07 PM.
Old Oct 20, 2010 | 08:05 PM
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Well the plugs in it aren't a month old yet. Kinda thought plugs should be changed with the cam and headwork. O2s I might replace with widebands anyway
Old Oct 20, 2010 | 09:34 PM
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Wide-bands? Then you are going to use emulation mode for the wide-bands to send a 0-1V signal to the PCM? You can't just plug a wide-band sensor directly into the stock PCM.... they have a 0-5V signal.
Old Oct 21, 2010 | 03:59 AM
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Ok then it is a little more involved than I thought What do you think about an o2 delete as part of the tune?

Last edited by wheelliftnpony; Oct 21, 2010 at 06:42 AM.
Old Oct 21, 2010 | 04:34 AM
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Originally Posted by wheelliftnpony
Ok then it is a little more involved than I thought What do you tinkering about an o2 delete as part of the tune?
If you're talking about running an open loop tune, that's fine (IMO) for a stripper car, but not so much on a street car. When properly setup using O2s will always yield better drivability and mileage.

Honestly though you should get it on a dyno and have it tuned.
Old Oct 21, 2010 | 05:25 AM
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More time "reading" is necessary

Originally Posted by wheelliftnpony
Well the plugs in it aren't a month old yet. Kinda thought plugs should be changed with the cam and headwork. O2s I might replace with widebands anyway
Originally Posted by wheelliftnpony
Ok then it is a little more involved than I thought What do you tinkering about an o2 delete as part of the tune?
IMHO, you are trying to "run" and you haven't even mastered "walking" yet.
Old Oct 21, 2010 | 06:40 AM
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Ok thanks
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