Runs loud/like crap when hot
 

Been lurking on the forum for about a week now after purchasing my 2004 AT RX8 two weeks ago. A little history on the car: has 48k miles, and was in an accident in 2006 but was rebuilt so it has a salvage title(so mazda warrenty is out for fixing it, i think).

So it's been heaven driving it for the first 10 minutes of my commute, but after that it runs like garbage. It pulls beautifully after 4500 until it heats up, then we're talking 30 second 0-60 times. I get this loud raspy sound as well, like embarassingly loud, and it's clearly comming from under the engine compartment. The wierd thing is that when it's cold it's no louder than it should be. The other thing is that it runs worse the longer it's driven. I took it out for a 3hr drive yesterday and by then time I was done it was starting to make the raspy sound as early as 3500rpms. It also seemed to have a tick, kinda like a HLA going out (I know we dont have them)

So to summarize

Running cold - runs beautifully
Running after 10 min into my drive - very little power above 4500k /w obnoxiously loud raspy sound
It also has a loud whistle when I hit certain rpm ranges with the gears. Off the top of my head, 4th gear whistles between 1600-2600rpm.

From looking over the boards, I dont think I have the marbles in a can problem. But with the performance loss when hot, I'm thinking plugs and coils, or else backed up catalytic converter. Anyone have any insight on this?

+1 for the catalytic converter. Guess you are not getting a Check Engine Light (CEL) yet? That should happen soon if it is in fact the CAT.

Ohhh boy, I am indeed getting a cel. Previous owner told me it was a bad gas cap so he replaced it and had the dealership reset the codes. It came back on 4 days later, so I assumed it was the gas cap.... That would be my bad

But why does it get so much friggin louder when hot and under accel? That part I dont get. What's happenning to make the volume change

Do you have a code reader or someone near you who has one?
where are you located?

Exhaust can't get out of the tail pipe...LOTS of backpressure. Your car is going into LIMP mode...it will not perform well and you will get horrible gas mileage and it is just generally unsafe.

You need to get your CEL read ASAP! Previous owner was feeding you BS. Once you can confirm that the CEL is related to the CAT, order a Hi-flow cat from a vendor here. They are nice since they are still legal (emission wise) and will provide moderate performance gains while still being cheaper than an OEM Cat (~$1,000).

Good luck

Located in waukesha WI. Cool bud, will do

You might even be able to find a used Hi-flow cat on the forsale boards here. that is how I found mine...I paid ~200 for it used and has lasted me about 2 years so far.

Will do! But in the meantime, is it fucking up my car!? Should I be worried about it drastically decreasing my engine life?

Oh, and would this be the guy I need?

https://www.rx8club.com/rx-8-parts-sale-wanted-44/exoticspeed-high-flow-cat-199040/

The same thing happened to me around 25-30k miles. Dealer gave me the run-around for about 2 weeks until I refused to pick up the car until CEL was gone. I'm now at 80k miles and running as good as ever.

It is a good sign that your car is still running well when cold, at least. You could probably make your own test-pipe by removing the CAT and "clearing out" the bad catalyst with your choice of tools...broom handle, long screw driver, etc.

Removing the catalyst from inside the CAT may alleviate this problem but will bring about another CEL for running with no CAT, but that would be a better option in my opinion. You could do this at least until you get a new Hi-flow CAT.

Yeah...that would work, but it appears it may still throw a CEL.

I have a Rotary Performance Super Cat and really love it. I've never had a CEL from it and it does a pretty good job of keeping the exhaust in manageable levels...the wife has not complained of it once.

Hmmm, may have 2 problems on my hands... Got codes pulled during lunch and this is what showed up: P0455.... Evap emission large leak. Which upon my 2 minutes of googling appear to either be the gas cap(not likely as it is a brand new one), purge valve, or broken evap hose. Looks like take to the dealer for an evap test is the best option.


EDIT: but I dont think something like this would give me the crappy performance I'm experiencing...
There was no code for the catalytic converter either.

Heh, double edit: Found a thread with similar problems where code for leak popped up but it was the cat. Gonna be working on it later today

Thanks Odddood, I'd give ya karma if I could!

See if the cat is covered by warranty. 80,000 miles I think Federal mandate.

Car has a rebuilt title, I doubt mazda will cover it

emissions equipment might be different.

dont mention the rebuilt title and try to get them to cover it anyway.

Hmm, car still is having trouble. It sounds nicer with a highflow cat on, but when it heats up it has a loud raspy sound above 4500rpms. Early in the drive, it only starts at 7k rpm and up, but if you keep running high rpms, it lowers the point where it does it. After a 3hr drive, it was doing it at 4500rpm.
Plugs were replaced 2 years ago, but the coils dont appear to have been swapped out. Going to try replacing the coils and hope that helps.

After that I dont tthink there is anything left but a bad engine.... and I hope to god that isnt the case

Would you say it sounds like either:

"marbles in a blender"

or

"lawnmower eating a rock"?

That's what kills me. I've heard the marbles in a blender sound from a member posted vidhttps://www.rx8club.com/showthread.p...arbles+blender, and I dont think it sounds like that at all. And it definatly doesnt sound like a lawnmower/rock scenario. It's unbelievably loud/embarassing as EVERYONE withing 50 feet of the car can hear it
It's a sickly raspy noise that only occurs when the engine has been warmed up and run hard. The first couple of times over 4500 are fine. After that it results in this sound.

I'll see if I can upload a vid to youtube and post it here.

Sounds like an exhaust leak

Yeah. The wierd thing though is that it only does it under load, never while idle.

My other observation is that the car smells different. When I first got it the exhaust had a sweet smell to it. After replacing the cat with a high-flow one(not sure if this makes a difference) it now has an acidic tinge to it and burns the nostril.

Still working on a video as my 3g does not record video...

Might be b/c under load the exhaust is physically shifting around.

Couple places to check:

1. Emissions Air injection gasket on exhaust manifold (right behind passanger's side wheel)
2. Donut fiber gasket between the new cat and straight pipe to muffler

The fiber gasket is a big pain if you don't have it and will produce noises like you are describing.

Also it sounds like you are having trouble with either your water pump or your radiator, because it seems that once it heats up its going into limp mode or something.

I'm having the same problem right now. I'm taking mine in for a compression check before I do anymore work on it. You should do the same. I tried new coils, new spark plugs, and switched out the stock cat to a midpipe. If it passes compression then I'll go from there.

It goes into the dealership tomorrow.
I took it there a couple of days ago and the service manager told me it was normal after I let him drive my car around town. Fucking idiot thinks power loss over time is normal!?! wtf... So I asked for their rotary specialist who actually races RX7s, so it should get resolved.

Keep me updated on your progress, would ya?

I took mine in yesterday and it passed the compression test. So I'm back to square one. Let me know what happens with your car.

check this out maybe it might help.

https://www.rx8club.com/showthread.p...check+radiator

My problem is apparently my upper intake manifold is cracked. GOnna be looking for a new one soon I guess as long as it's not that hard to replace