Uh oh.... Whatever it is you better act fast!

 

Man..people make out like your stuffing a sock in your Y-pipe or something. Most high flow cats cost almost no power. Matter of fact many mufflers..or even where the Y-pipe merges will create a bigger exhaust disturbance. I have run both off road and cats on my GTO which is in the 420 RWHP range..and it runs basically the same at the track. I may loose 1-2 HP or something..but you never notice. It is funny..in the GTO and Corvette communities 2/3+ of the headers we sell are bought with cats. In the F-body community almost no one runs cats. Generally...I find people who go off road do so because it is much cheaper than buying cats. Then they use the "It will make more power", or "It will be louder excuse" to jusify it. Around here there are several mechanics who will not touch a car without cats. Plus when yiou go to sell the car, your stuck putting cats back on anyway to get through inspection.

 

I don't think there is anything wrong with cats. I wouldn't replace them because I want the exhaust to smell better, though, I would just fix the leak.

-Geoff

 

its a leak start checking.

 

Are you running breathers in place of a stock PCV system? You could be getting blown by and smelling exhaust fumes through your breathers if you have them.

 

I've read these threads front to back and never found a fix for the problem. I could distinctly smell exhaust and burning oil through my vents and it was driving me crazy. My whole car smelled like it and I would smell the same way anytime I rode in it. I went through my exhaust looking for leaks, looked under the car for missing drain plugs, pulled the panels out along the dash and checked the firewall, and never found anything. I had my valve cover gaskets and oil pan gasket replaced and cleaned all the oil from the motor. Nothing worked or solved my problem. I took the car to a muffler shop and they found no leaks. I was at a loss and pretty frustrated.

I was looking under the hood along the firewall desperately trying to find an issue. Then I started looking at my cowl. I found on the drivers side where the cowl clips down right under the hood, there is some wires coming through a half circle plug. Right there was a half inch to a one inch gap along the cowl until the place where it tucks back in under the windshield. The fastener there was missing so I went to autozone and bought some. Even when fastened, there was still a gap. I took the fastener back out and I stuck my fingers in the gap and felt a badly damaged mostly missing foam weather seal. I cleaned that out and got some self adhesive foam weather strip from lowes. The thickest one that they had. I think it's 1". I stuck a piece lengthwise with the car as far back as I could. It's hard to describe but it basically goes straight in there along the cowl following the finder from front to back. It goes about 5 inches back there. Then I ran a piece along where the old seal used to be as far as I could before the cowl seemed better sealed. You'll see that the cowl has a piece of plastic that comes down to touch the plastic below it. You want your foam right there. I used a nut and bolt to clamp it down tight instead of a plastic fastener and finally solved the problem.

As far as getting that freaking smell out of the car, it's a process. I have the rare SS blessed with cloth seats (yes it exist). So, mine was really tough. Buy a chlorine dioxide odor eliminator and run that for 24 hours. Run your AC on Max (recirc) for 15 minutes then let it air out. Pull out your front seats. You could pull the back ones too, but because they flip down, I didn't. Get yourself a carpet cleaner with an upholstery attachment. If you don't have that, you can use some carpet cleaner solution in a spray bottle and a shop vacuum. Start with the front seats and clean every side thoroughly. If you don't have a carpet cleaner use a brush to agitate the upholstery after wetting it with your solution and use the shop vac to remove it. You will be stunned at how dirty your cloth seats are when you see the grimey water coming out from where you sit. Do every inch of carpet especially in the floorboards. Do the back seats then flip them down and get behind them. I used an odor eliminating carpet shampoo for pets. I even hit the cloth door panels. For the headliner and rear hatch where its got that weird short kind of carpet, I sprayed those areas with Febreze odor eliminator (also for pets), and rubbed them down with a clean terry cloth towel. You really should hit the floors and front seats twice if you want the best chance of success. Let the car air out and dry. Put your seats back in. Be careful with your front seats to not scratch up the plastics on the side of them. I jacked my passenger side up pretty bad in my driveway. Lastly you can get an armor all smoke eliminator. Set that in the cup holder, start the car, run max ac and activate it. Close it all up and let it run for 15 minutes minimum. Air it all out and enjoy. There's a combination of smells at that point but none are smoke or exhaust.

 

Thank you for finding and providing a solution after all this time!

 

I'm older so as a kid I remember all the cars (pre 1975) that didn't have cats. Ya'awl make it sound like all pre 1975 and anything newer that had cats removed or gutted will smell like exhaust. I say ya'awl are crazy. Cats don't remove exhaust smell. They only convert NOx's to less harmful compounds. Back then and still to this day, if you smell exhaust it ain't cuz of cats. It's because you have a leak or the exiting exhaust is routed in such a way as to accumulate under the chassis and then leaks into the passenger compartment. If there is no leaks then it's where and/or the angle of the exhaust tips. Make the tips parallel to the horizon exiting past the rear axle AND not under any body panels or bumper.

Now for the cats themselves, in a vehicle that's not mostly @ wot (ie not strictly a race car) and is computer controlled you need some backpressure. Without backpressure the O² sensors won't work properly. On anything not fuel injected (ie LS 427 crate engines) and have a carburetor ANY backpressure will reduce HP. How many NASCAR or NHRA super stock - top fuel drag cars have cats or even mufflers? Only if state laws restrict noise, but all others run straight pipes. Cats also add weight compared to an equal length of exhaust pipe.