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2nd Gen Ram Tech 1994-2001 Rams: This section is for TECHNICAL discussions only, that involve the 1994 through 2001 Rams. For any non-tech discussions, please direct your attention to the "General discussion/NON-tech" sub sections.

o2 sensor question with no cats..runs rich?

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  #1  
Old 10-27-2008, 03:24 PM
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Default o2 sensor question with no cats..runs rich?

Ok my truck has hedman headers, cat deleted, and flowmaster original 40 series.....no check engine lights...Its a 2000 5.2l so theres a pre cat o2 and a o2 after the cat.....since i deleted the cat the truck has run much richer and obviously a decrease in performance...the only thing that would be effected by a cat delete would be the o2 after the cat and i didnt think that controlled the air/fuel ratio? or does it play a small part? does fastman still sell o2 sims?
thanks
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Old 10-27-2008, 03:43 PM
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http://www.thefastman.com/02Simms.asp

for sum reason the rams with two o2's before and after the cat, they like to make problems with the deleteing the cat.( i think it the after cat o2 that get the bad reading)).... older rams just have one before the cat and don't seem to have the same problem.... also you may have damage the o2's..... but if it was me i would buy the slim's.... i wish i had a OBll so i could use the slims

hoped i helped... tell us what you end up doing
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Old 10-27-2008, 06:41 PM
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You are correct in assuming that the post cat O2 sensor does not determine the A/F ratio, it merely asseses whether the cat is doing its job.

What leads you to believe its running rich? Smell?

If you're going off smell then you're probably just noticing what exhaust smells like without a cat. If you're really running overly rich, you may have damaged (or it may have just started acting goofy) your front O2 sensor. I'd clean or replace that and see what happens.
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Old 10-27-2008, 08:16 PM
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yea i understand you get a smell without a cat...its running rich because it gives alittle more sooty residue than usual, and a under harder accelleration alittle dark colored smoke, so yea its running rich i think im still going to SIM the rear though any other input?
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Old 10-27-2008, 08:58 PM
jakemary jakemary is offline
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yes fastman has the o2 elemator . but the rich smell might be your nose over acting with no cat.
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Old 10-27-2008, 10:25 PM
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i appreciate everyones input but i know what cars smell like without cats...im just saying it shouldnt be producing black smoke, aka running rich, unless im missing something here?
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Old 10-27-2008, 10:41 PM
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Mine does not produce black smoke on accel, that's not normal. It didn't when I had no cat either. However, my tips do have black soot on them on the inside and on the lip. That is pretty normal.

Like I said though, you need to check your front one, its the one that controls the A/F ratio, not the rear. Sim'ng the rear isn't going to help that, it will get rid of a check engine light for poor catalytic efficiency though.

Other things to check would be your plugs and wires if you haven't done a tune up in a while that might be in order as well. However, I still lean towards the front O2 sensor giving a misleading signal to the PCM causing a slight rich mixture. That wouldn't throw a code, wheras a signal thats WAY off would.
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Old 10-27-2008, 10:49 PM
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ok thanks, i have no check engine light, its only every once and awhile during almost WOT accelleration that it will smoke alittle black, it never smokes black during normal driving...i appreciate the help. plugs and wires are fine too.
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Old 11-23-2010, 07:56 PM
97ramlv 97ramlv is offline
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Cool driving without cat.

Is it ok if i drive without my stock cat for like 2 weeks until i get my new magnaflow one? Thanks.
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Old 11-23-2010, 08:31 PM
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Quote:
Originally Posted by 97ramlv View Post
Is it ok if i drive without my stock cat for like 2 weeks until i get my new magnaflow one? Thanks.
i may run a little rich, and get a code,,,,,,,,,,,,, or not


also a thought
http://dodgeforum.com/forum/2nd-gen-...converter.html
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Old 10-20-2012, 11:55 PM
gregadams6412@sbcglobal.net gregadams6412@sbcglobal.net is offline
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i dont think the downstream (rear) o2 sensor has anything to do with the trucks air/fuel mixture. its just there to make sure that the cat is working good, and to throw codes when people try to remove them lol. i cut the cat off of my 01 ram 318 and put 2 spark plug non foulers onto the downstream o2 sensor. works perfect. truck doesnt run rich, plugs dont get fouled out, and best of all, no check engine light. google/youtube the spark plug non fouler trick
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Old 10-21-2012, 12:00 AM
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The upstream O2 helps determine air/fuel mixture. If it is gone you run rich.
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Old 10-21-2012, 10:14 AM
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It was determined by a member here (cant remember who) about a year or so ago that the post cat o2 does play a roll in a/f mixture. It doesnt do a lot, but does have a slight impact on it.
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Old 10-21-2012, 02:01 PM
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Quote:
Originally Posted by kejobe View Post
It was determined by a member here (cant remember who) about a year or so ago that the post cat o2 does play a roll in a/f mixture. It doesnt do a lot, but does have a slight impact on it.
I remember hearing that too somewhere, like you said it didn't determine much at all but did have a slight impact on the a/f mix
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Old 10-21-2012, 02:28 PM
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It does have a very minor impact on A/F. Non fouler is not enough to throw it off by much if any at all. And IIRC, the member that was experimenting/researching it is drewactual .
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Old 10-21-2012, 03:27 PM
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Yep thats the guy! I could picture his avatar but not his name, lol
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Old 10-21-2012, 03:30 PM
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Quote:
Originally Posted by Ramcountryboy View Post
Yep thats the guy! I could picture his avatar but not his name, lol
Ok, now read the other thread where I ask what part of NH you live in.
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Old 10-21-2012, 08:32 PM
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Hmmm, and where would I find this thread? I even searched for it
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Old 10-22-2012, 10:32 AM
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hmm thats strange i didnt know that! but good to know too! with that being said i may just go ahead and get a custom tune. my truck needs it anyway with a CAI and no cats. thanks for the replys!Click the image to open in full size.
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Old 10-22-2012, 04:53 PM
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I'm thinking your truck does not need a custom tune for a CAI and no cats. Just needs the o2's in the correct spot's and a non fouler(s) for the downstream o2's and canned tunes.
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Old 10-22-2012, 04:53 PM
 
 
 
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06, avenger, cat, cummins, dodge, engine, o2, oil, post, ram, rich, running, sensor, sim, sooty

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