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is it norm. to have a strong smell of gas to come from the exhuast?

taman86

taman86

New member
to finish the title, is it normal to have gas smell coming from the exhaust when running an aftermarket exhaust. not too familiar with gp's, ls's mostly and it is normal when going to headers or removing the cats. to be more specific my 97 gtp has flowmaster exhuast and nothing else done to the exhaust, so stock headers, dp, cat. its noticable just about anytime its running, so driving or ideling. anybody else have this issue or any thoughts on this?
 


You shouldnt be smelling any gas from the exhaust if you still have a cat.
Now, if the exhaust is brand new, you will have a burn-in time typically, in which you get some strange smells..but it goes away after some heat cycles...
 
maf would throw a code.

next question, is it throwing any codes? misfires? check your plugs and wires, you might have a dead cylinder and unburnt fuel coming out the exhaust
 


no codes, and runs fine besides bogging sometimes which im discussing on another thread which i have been lead to be a possible plugged cat. but other then that, not codes, no missfires
 
well that would be the reason. it probably messed up the post-cat o2, so it's sending a bad reading and the pcm is making you run super rich
 
Ooohhhh ok, so if its clogged then its not allowing the post cat o2 to read correctly and since its not reading correctly its trying to compensate by adding more fuel cuz really its only reading air not burned fuel. I get it, so cat it is
 


Im sorry for cuting in but it seems that his problem has been solved.
I have the same problem but with no boging down. I only smell gas when it just started or its running cold.

what would cause this by the way the car has back fired from a bad plug but all plugs have been replaced
 
Well, if you have no catalytic converter, its normal to smell some gas.
If you do though, you're probably running a little rich.

On start-up, you will smell some, because the cat isnt hot enough to do its job for a tiny bit.

Could be a bad o2 sensor.

Now if it's a very strong gas smell, then it's running rich as hell.
 
possibly an ignition issue. check your wires at the coil packs and spark plugs, pull the plugs out and see if one is discolored and such.
 
the smell is pretty strong outside the car for a couple mins after starting.
One of my mods are a ported tb, but that should make it run lean.
today im going to try to get my dhp working and after that i will pull the plugs again[last time one got damage from high heat]
 
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Hang in a second guys. The downstream o2 (one after cat) does not control any fueling at all in 97-03 car. It has one purpose, to monitor the emissions. That's all. It can only post a code that makes you fail emissions.

Your front sensor in the rear exhaust manifold can get lazy etc and cause you to get too much fuel. That should then murder the catalytic and trip the code for poor emissions, based off the reading from the rear o2.

Since you have some bogging, it's possible you have a clogging cat from the excessive fuel.
 


BillBoost37 said:
Hang in a second guys. The downstream o2 (one after cat) does not control any fueling at all in 97-03 car. It has one purpose, to monitor the emissions. That's all. It can only post a code that makes you fail emissions.

Your front sensor in the rear exhaust manifold can get lazy etc and cause you to get too much fuel. That should then murder the catalytic and trip the code for poor emissions, based off the reading from the rear o2.

Since you have some bogging, it's possible you have a clogging cat from the excessive fuel.
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Thank you for saying this!! I was thinking the whole time that their down stream O2 wouldnt decide fuel trims.. I was getting lost in my own thoughts
 
Hang in a second guys. The downstream o2 (one after cat) does not control any fueling at all in 97-03 car. It has one purpose, to monitor the emissions. That's all. It can only post a code that makes you fail emissions. Your front sensor in the rear exhaust manifold can get lazy etc and cause you to get too much fuel.
Click to expand...

What?! if the rear 02 doesnt do anything but throw the code then it wouldnt be there. the front 02 is more then effective to do that by its self if it is running too rich or too lean for an extended perior of time i believe. the pcm is programmed to read the 02 within a preset limit. if the rear 02 isnt reading what the pcm is programmed to read such as running lean then the pcm will add fuel, not the 02 my bad for posting that above. now that being said i can see where you said that it throws a code, cuz if its reading out of limits after the cat then it should throw a code, not the front.
 
try figuring out a code on a 4th gen f-body v8. 4 02 sensors, 75 bucks a pop just to figure why its getting "lean conditions on left and right oxygen bank". change all of them, reset computer, drive for 10 minutes, ses light, same thing. change the cats or go cat-less and get 02 sims or have a buddy with hp tuners erase the code from the computer :)
 
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