5th Generation Maxima (2000-2003) Learn more about the 5th Generation Maxima, including the VQ30DE-K and VQ35DE engines.

For people running Headers or Gutted Precats.

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Old 05-05-2012, 03:09 PM
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For people running Headers or Gutted Precats.

I have no cats in my car. Pre or Main cats. The fumes are driving me nuts. Do any of you guys run into the same problem? If I install my Main Cat will that cut down on most of the fumes? Or is it running PIG rich? MPG's where 18.7 at last fill up and that is 100% city driving so I think that is good. Would running an Apexi FC and getting it tuned get rid of the smell?
1. Its coming from the Exhaust.
2. Started to smell when I gutted my pre Cats.
3. Does not smell inside of car.
4. I am running Plug foulers on the secondaries. 2 on each with the 1st one having a 1/2" bit ran thru it.

Well what do you guys think?
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Old 05-05-2012, 03:16 PM
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You must have a leak, although, Idk why you wouldn't hear it.

No fume problem on either that I've owned without cats. Even standing behind the car it smells fine.
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Old 05-05-2012, 03:29 PM
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Check to make sure your flex pipe isnt damaged and there are no leaks. Just got my flex replaced last week and that got rid of the exhaust fume smell in the car
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Old 05-05-2012, 03:39 PM
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I had the gutted precats and fastcat and 3" Exhaust it wasnt a major smell, only if you are standing right behind it and is the same way with Headers now, it will cut down the smell some if you put the main cat back in there though....GL....
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Old 05-05-2012, 03:51 PM
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What does it smell like? Rotten eggs or are you running pig rich.
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Old 05-05-2012, 04:58 PM
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I have v2 headers ypipe and test pipe. No cats and it smells fine. If you stand right behind the muffler you can smell it. While in the car though it standing anywhere except the back you cant smell it. Check for leaks.
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Old 05-05-2012, 05:25 PM
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i have strong fumes as well omg i have 02 with obx headers 2.5 straight pipe exhaust full bolt ons with G35 injectors and i smell the 93 gas so strong i think im running really rich
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Old 05-05-2012, 05:42 PM
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no cats will cause a more potent gas smell. Thats what cats are designed to remove. There is nothing you can do to fix that other then installing a main cat. when I installed my headers it was the first thing i noticed. I am use to it as my other car is catless and boosted

a piggy back tuner wont do anything below 3k and 50% throttle. Ecu controlls that 100%. A bad maf might cause a rich idle.
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Old 05-05-2012, 07:20 PM
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What about running a high-flow catalytic converter? You know those types which claim to be hi-flow and not rob power.. etc.
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Old 05-05-2012, 09:01 PM
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Yeah I figured the removal of all the cats would cause it to smell. It does not smell in the car and I smell it when I am stopped and a wind blows it towards my open window. I am too.g to install the main cat and see if that helps. It should help a bit. Again if I stand behind my car I can smell it. I am positive it is not an exhaust leak.
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Old 05-06-2012, 05:07 AM
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The main cat does most of the conversion. As long as the main cat is in place, just gutting the pre-cats alone won't cause any smell at all.

Put the main cat back in, or buy a Fast Cat, and you'll be fine.

...unless you have a leak.

Last edited by Rochester; 05-06-2012 at 05:09 AM.
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Old 05-06-2012, 07:24 AM
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Originally Posted by Rochester
The main cat does most of the conversion. As long as the main cat is in place, just gutting the pre-cats alone won't cause any smell at all.

Put the main cat back in, or buy a Fast Cat, and you'll be fine.

...unless you have a leak.
No leak. I went thru that already. After I put the Pre cats back on I did not reinstall the front Pre Cats heat shield. I did not realize that the bolts go ALL the way thru into the cavity! I drove for an afternoon like that till I reinstalled them. I'll slap the Main Cat back in tomorrow at the shop.
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Old 05-06-2012, 07:56 AM
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That's what happens when you do things illegally......................................... .............................................
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Old 05-06-2012, 09:09 AM
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Ive got gutted cats, with a main cat intact. I remember thinking it was running rich for the same reason, but I have a bad exhaust leak right now. Which will be remedied when my cattman y returns from repair, I'll check back once it's installed. I almost suspect the manifold gaskets needing to replaced, to the point where I actually got some last year.
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Old 05-06-2012, 03:49 PM
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I've run with no cats at all, and now no pre cats and a Cattman Fast Cat. Never smelled any fumes.
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Old 05-07-2012, 02:36 PM
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Installed main cat again. No more stinky! But I lost a bit of the rumble when decelerating.
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Old 05-07-2012, 02:41 PM
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Originally Posted by Xpcgamer
Installed main cat again. No more stinky!
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Old 05-07-2012, 02:44 PM
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Originally Posted by 03BlkSETE
I've run with no cats at all, and now no pre cats and a Cattman Fast Cat. Never smelled any fumes.
I have to agree here, not because I've experienced it, but I thought my fume issue would have gone away with the FastCat, but it didn't.

I need to look into my problem a little bit further. Been smelling the fumes quite a bit lately, I may need to tighten up some exhaust items, hopefully it's not a loose header, or leak in that area. I would imagine if it was, I'd hear it. And my issue happens more when in recirc mode and when the fan is on. I may need to do the old fashioned vent purge with Lysol that was so popular a decade or so ago.

Strangely enough it actually smells quite a bit like what we smell when we use breathers (oil/gas, blow-by).

I'm going to try a little something different with my PCV lines to see if that helps.

I was thinking I may have had my breather in an area where my cabin fans were sucking up the smell, and sending it back into the cab, hence my noticing it.
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Old 05-07-2012, 02:57 PM
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Only smelled fumes when I had exhaust leaks (OBX>High Flow>Cattman 3")

After I fixed the flex pipe, no fumes at all.
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Old 05-07-2012, 03:11 PM
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Originally Posted by aackshun
Only smelled fumes when I had exhaust leaks (OBX>High Flow>Cattman 3")

After I fixed the flex pipe, no fumes at all.
Might be my problem. Any noises associated with this alleged problem?
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Old 05-07-2012, 03:44 PM
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Well mine started a very minor rasp to a annoying BAHHHHHHHHHHHHHH all the time (went from a fray to an actual hole in the flex).

goto my youtube (Djairman) and browse some of the last videos on it before the track day. You'll hear how loud it was when it was a straight up hole.
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Old 07-15-2012, 04:19 PM
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Well, my V2s were just installed and I'm smelling major fumes when I'm about to take off at a stand still, my poor girl was holding her breath haha, but I'm thinking the flex is bad, it's frayed a bit and it sounds like it has a slight leak. I also need to put the heat shields back on soon.
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Old 07-15-2012, 07:16 PM
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After I installed my main cat it still smells a bit when the car is cold. Once the car heats up the smell is gone. I figure the cat gets hot and starts working so the smell goes away. I mean a lot of raw fuel does not get burned in motors which is the fuel smell you get.
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