2nd Gen Ram Tech1994-2001 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.
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?
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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
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.
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?
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.
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.
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