maxinout93

My 02 i35 was kinda slow at times. SO yesterday I went and gutted the firewall precat. Now i start the car up and it runs ok. But as soon as I press the gas pedal. I hear a loud whoosh sound every time. Sounds like air but very loud. The car barley will drive and seems it has no power. Could this be an exhaust leak or something else. It drove fine without the air noise before i gutted the precat smh.

DennisMik

iTrader: (2)

You have an interesting problem. First, you describe the air sound as a "whoosh". To me, a whoosh sound is not a loud sound, an exhaust leak would be louder. However, sounds are subjective to each person. When the engine is cold, start it up and check for exhaust leaks around the pre-cat at the connection flanges and the O2 sensors. You will have a couple of minutes before the pipes are too hot to touch. Also check the flexible joint where the y-pipe forms the y.

But an exhaust leak should not cause a no power situation. Did you do any other work at the same time, like on top of the engine around the throttle body or MAF? In general, looked for unplugged /broken wires in the areas you worked in.

maxinout93

Yes I only gutted the pre cat and removed the y-pipe. I broke maybe a stud upon removing the y-pipe to firewall pre cat and see a little gap there also it was a gap in the radiator side pre cat connection. Going to get those bolts today. But whenever I start the car I hear the air sound, and much louder when I accelerate. I could not get the car to go over 40 mph. Everything was fine until I did the pre cat. I'll prob take the y-pipe off to be sure nothing fell in there clogging it up.

maxinout93

The car starts right up now and it's not loud though when it runs, it's jus a whoosh or loud hiss.

Child_uv_KoRn

iTrader: (7)

Gut the other two and maybe you'll fix the problem lol

maxinout93

Both pre cats are now gutted, havent messed with the main cat. I gutted the radiator side last year, and the I bought a new firewall precat 2 years ago. So i Just gutted that one yesterday.

Child_uv_KoRn

iTrader: (7)

Pedal dance reset. Kinda sounds like a tiny leak (not that it should affect anything). If they do visual inspections for emissions, then gut the main cat, otherwise, you can get a test pipe and scrap the cat for cash.

maxinout93

ok I will do that, I went to get some screws from lowes, and only managed to get one in because of the rain and getting dark, still hear the air noise and exhaust a little loud/ deep still having the acceleration prob but see a good little gap in front pre cat to y-pipe bolt. managed to get it to 50mph with a struggle, but dont want to push it.

Child_uv_KoRn

iTrader: (7)

Copper RTV at the flanges, especially on that front compression one. That will definitely leak, but RTV makes it all better (been there done that myself).

MadMax07SL

You sure the whoosh you're hearing isn't a suction leak? maybe you disconnected a few suction hoses to get room, and either didn't connect them all or have a damaged tube. I can't imagine how an exhaust leak could keep the car from getting above 40mph....it has to be something else going on, unless like someone said, you have clogged the exhaust further down with debris...

maxinout93

No i dont think there are any hoses other than the coolant hose on the oil cooler down near there. IM thinking something may have fallen in the y-pipe possibly while i was gutting the firewall precat. I dont know where the air sound came from either.

TallTom

Since you moved the y-pipe, check the flex pipe for any cracks.

maxinout93

I took the y-pipe off again to be sure there was not anything in there blocking the flow, then bolted it back up. So now i still hear air when i accelerate and also upon starting the car. Its like the air fuel mixture is way off i can barley drive it, no power at all. So I know the front pre cat( radiator side) is only being held on by the two studs on the exhaust manifold, because the other 4 broke off, and also no gasket is on the front cat to manifold or front cat to y-pipe connection. Also the rear pre-cat to y-pipe has 2 bolts holding it on and a decent size gap from the 3rd bolt not being on there. Also rear pre-cat gasket is bad to y-pipe. I did notice flex pipe mesh is tearing apart, but i dont know if its leaking exhaust, But i know im smelling exhaust in the car more so now than before i gutted the darn pre-cat. I may see what an exhaust shop will charge for this, Although i created the problem I still dont want to spend $250 for bolts and gaskets that Midas quoted me.

maxinout93

OK things havent really changed much. I took the car to a midas shop today. THey told me about not really anything was coming out of the tailpipe and the system is severly clogged. What can make it clogged though? Only thing i can think of is the main cat is clogged?? But how when it wasnt that bad before i took the stuff out of the second precat. They say there is alot of backpressure. I dont know who to believe, but i do know both front precats are gutted, they may have leaks at the y-pipe im not sure but majority of the loudness comes from the front of the car not the back. If there is not very much exhaust flow coming from the tail pipe, then where is it going? Could a combination of exhaust leaks and a clogged main cat cause my issues, currently cant drive the car fast as it has no speed due to exhaust issue.

Child_uv_KoRn

iTrader: (7)

I told you to gut the main cat..... If it's clogged, then all the pressure is making leaks in the exhaust where you ****ed it up lol

Heavily copper RTV all the ****.

maxinout93

lol u might be right man, im assuming the main cat was the problem before i gutted the firewall cat and once i did that more exhaust is flowing thru creating more backpressure making the car almost undriveable smh. Only thing is my main cat is welded to the catback but not the y-pipe. The guy at midas was kinda giving me a hint about that but he didnt come out and say it because they couldnt do it here in nc, but im in sc with no emissions.

Child_uv_KoRn

iTrader: (7)

What happens is the precats fall apart and if it doesn't ruin the engine first, then it clogs up the main cat. Been there done that at 75k miles and it blew the engine at the same time.

You'll probably have to cut the cat off, but you can knock out the studs and put bolts in if you're gonna gut it. Unless salt isn't used where you are...in that case, **** you lol.

maxinout93

But is there a way to tell or test if the main cat is actually clogged?

CMax03

iTrader: (3)

Sounds Like an exhaust leak to me....

maxinout93

Yeah but the shops are telling me the main cat is clogged because of very little exhaust from the muffler. Now before i did anything the car was ok pretty much, had a small rotten egg smell and slight power loss when really getting into it. Now im assuming ive created a series of leaks that were not there before. One being the from cat at the top by radiator with only 2 studs holding it on, and 2 at the firewall precat and y-pipe connection. Shop telling me main cat is clogged and wants $350 to replace it, they say backpressure is high because of clog so im afraid to drive it more than a 5 miles as it will take forever to get up to speeds of 55mph. So they told me if i seal the openings in the exhaust then that will make things worse because the pressure will then go back into the engine??

DennisMik

iTrader: (2)

I guess the test would be to unbolt the y-pipe from the main cat and start the engine and see.

CMax03

iTrader: (3)

Disconnect the exhaust at Ypipe to cat flange and visually inspect your Cat substrate material...My truck did this same thing and the substrate broke and was clogging up the air flow....Cats are cheap contact Warpspeed $100 approx....with flanges

maxinout93

Thanks man I will look into it either today or tomarro or possibly this weekend. Come to think of it I do remember seeing stuff like a peice of mesh inside the main cat when i took the y-pipe off.

maxinout93

CMAX03 and CHild uv korn you guys were right!! The main cat was indeed clogged. I drove the car to work this morning and when i got off i took it to a shop and i was not sure if they did exhaust work, long story short, they informed me of the backpressure that was making the car almost impossible to drive. I havent driven the car in almost 2 weeks so it pretty much sat until i figured out what was going on. They said since i live in a non emission state, they would cut the pipe at the rear of the resonator and see if the engine breathes better, long story short they ran a straight pipe from the main cat and deleted the resonator even tho i didnt want to really remove the resonator, but maybe a possibility it was clogged too. So now I still have a leak at the y-pipe and firewall precat connection but ill take care of that. All i know now is i can now DRIVE MY CAR, and fast too!! later on ill probaly go back and add a resonator. I serously did not know that a catalytic converter could almost make a car undriveable like it did mine. I honestly thought something else was wrong because I gutted the rear pre cat while it was still attached to the car. But now it hauls *** like its sopposed to, just a little louder but ill fix that later. And MOst of all there is no more air sound when i accelerate. The theory u guys were talking about is true here, the cat was clogged, and the air sound came from exhaust gases escaping from what ever leak they could get out of, and also the reason for barley any exhaust coming out of the tail pipe. Thanks for everyones responses!

Prophecy99

iTrader: (1)

nice update !

maxinout93

thanks man almost feel like i have a race car now lol.

cdoublejj

it's nice to have the follow up information +rep!

maxinout93

thanks man.