LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Running rich

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Old 08-03-2009, 10:32 AM
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Default Running rich

Well sometimes when I start the car up its like it won't leave closed loop or open loop, whatever it starts in. On the A/F gauge its pegged in the green, last notch. Its a Autometer narrow. Other times the car runs normal, but sometime during the trip it goes back to all rich. When it does this you can smell it even. They are AC Delcos o2s with only 15k miles on them. What can be causing this?

Car had been dynotuned back in January I think, and had been running great. This issue seemed to come up last month when I drove to PA, I noticed it doing this on the return trip a lot and randomly as I drive it through the day.
Car feels slower when running that rich, when its not running that rich well it feels good like it used to. I just don't get why sometimes it doesn't do it, its not a constant problem, but its annoying.
Old 08-03-2009, 10:37 AM
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What you do to it fool?..


Maybe it's the MAF going out.
Old 08-03-2009, 10:38 AM
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Hmm I have some MAF cleaner out there, maybe I will pull it and see what it looks like.
Old 08-03-2009, 05:41 PM
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Well? What could cause it to run rich? Also no SES light.
Old 08-03-2009, 06:16 PM
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i had the same prob a few months ago. i checked my fuel trims and bank 1 long trim and short trim were maxed out rich!!! it was so rich it would burn my eyes when i got out of the car. anyways, i changed the oxy sensor on bank 1 (drivers side). fixed the prob immediately. so, put a scan tool on the car and see where it is running rich at. if it is the problem is restricted to either bank it is probably an oxy sensor. good luck...
Old 08-03-2009, 06:19 PM
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Hard to tell, but I do have the narrow gauge hooked up to the driver side. I know in Autometers instructions it says if a o2 sensor fails it will show up pegged rich. I just don't understand why I would have a failed AC Delco at 15k.

Can I see the parameters you are talking about in freescan?
Old 08-03-2009, 06:27 PM
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yea i believe so... try this...switch oxy sensors. move driver side to pass side and driver to pass side. if ur gauge reads ok it is the oxy sensor
Old 08-03-2009, 07:20 PM
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Is this the same car with the code 36?
Old 08-03-2009, 07:53 PM
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No this is my car acting up with the rich issue. I just drove to Advanced auto parts, didn't run rich like I was describing. I also wasn't running my A/C on this little voyage, but I can't imagine that factors into this.

The code 36 car is my Mothers. She has had the car less than a month. Sent to PCM out to Ion to get a decent tune in it as the tune that was in it when bought wasn't right. When that came back well now I have a code 36 on that car.
Old 08-03-2009, 08:18 PM
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Your first problem is that you're using a narrow-band O2 gauge!
Old 08-04-2009, 05:06 PM
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Anyone else ever have AC Delco's die at 15k?? I hear some people say they get lifetime warranty on the Bosch's or is that just the LS1 sensors?

GMpartsdirect probably doesn't have a warranty do they?
Old 08-05-2009, 12:07 PM
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Also do different exhaust setups affect o2 life? I've got a single 4" now. I'm just wondering why the hell I probably have a bad AC Delco at 15k?
Old 08-05-2009, 12:10 PM
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Originally Posted by camar0corey
Also do different exhaust setups affect o2 life? I've got a single 4" now. I'm just wondering why the hell I probably have a bad AC Delco at 15k?
You didn't use them with brand new ceramic coated headers did you?
Old 08-05-2009, 02:24 PM
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More than likely he used my old Headers..
Old 08-05-2009, 10:12 PM
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I did use your old headers.

So today it was fine. I haven't messed with the car at all and today it didn't go pig rich. It's kind of aggravating. Hopefully when I drive it tomorrow it will still be normal. Its one thing if you made a change and the problem went away, but like I said I haven't touched a thing and it ran properly today.
Old 08-11-2009, 01:08 PM
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Alright here are some pictures.
Driver side o2




Driver side plugs


Passenger side plugs


Passenger side o2 sensor




I had this metallic dust from both sides, I'm going to guess dried out anti-seize?


The plugs and o2s have approx 15k on them. I put in new plugs gapped at .050 today. Those plugs in the pictures were gapped at .045. Interesting enough Chiltons says the gap is supposed to be .035 and Haynes says .050.

I have the narrow band gauge hooked up to the wire going into the PCM for the driver side o2 sensor, the purple wire or purple with white stripe I think, whichever one it is. I won't have a wideband til I can afford one, going to get one for the nitrous. Still it can tell me when its running pig rich. No light show that everyone likes to harp on, well I wish I had the light show. It is just pegged out on the rich side, won't move. Other times I take it out after it warms up it runs normal.

The_Merv suggested the MAF above. If the MAF is on its last legs or dead, will the car run rich?

Last edited by camar0corey; 08-11-2009 at 02:42 PM.



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