Dude_Trust_Me

Hi everyone!

Here is a little background of my issue:

I have an 04 Manual RX8 with 105K miles and for a while now I am unable to drive the car for more than about 20 minutes or even take the highway. There is an extreme power loss after the car gets "warm" and frequently stalls when coming to a stop. This issue also happens in less time if I drive the car more aggressively. Now, I am able to start the car and keep driving after it stalls but the issue continues until the car is cold again. If I drive the car smoothly and accelerate slowly, the issue does take a lot longer to happen.

Please note that if the issue doesn't happen and the car gets hot, and I turn it off, it will start with no problem. (I understand that slow starting when warm is a sign of weak compression)

Also, I get frequent misfires (flashing CEL) if I accelerate past 5500 - 6000 RPM. I have attached a picture that I took of my cat, does that seems to be the culprit? Or at least not "normal"?

List of things I have already changed:
• Fuel Pump
• Ignition Coils
• Spark Plus (one of them was actually broken when I removed)
• Spark Plug Wires

Thanks for your help!

Loki

iTrader: (1)

That cat picture doesn't tell us anything, you really need to take it down and examine the interior. But, all the signs point to cat failure, yes. Since one spark plug was broken, there's a very good chance poor ignition killed the cat.

If you do replace the cat, go with an original Mazda one or a quality HJS high flow one. It will be expensive, but cheaper off-the-shelf replacement cats don't live long attached to a rotary. Normal operating temp of our cats is around 1800F.

Potentially the previous owner welded in just such a cat after his original one bit the dust. The one you have there doesn't look original (if only because the welds are pretty gnarly).

dannobre

iTrader: (3)

What kind of CAT is that?

Most aftermarket ones dont last too long in a rotary engine

UnknownJinX

You need to take it out and look inside to be sure. It doesn't look like a high quality aftermarket cat to me.

If the aftermarket combo is not more expensive than OEM, it won't last.

furansu

My stock catalytic converter looks great from the inlet pipe. I removed the o2 sensor and found some small pieces were breaking away and that the second section of the catalyst was about 50% clogged (using a scope camera).

You'll want to buy a high-quality catted pipe if your area requires emissions testing, or if you don't want to smell like you just finished mowing the lawn when you go for drives with the windows down. -- if getting a cat welded in, make sure it is a quality metal converter, rated for high-temps. Random makes performance catalysts that are fit for high HP and temperature operation.

Dude_Trust_Me

Thanks everyone for your comments and suggestions.

That is I believe a Magnaflow cat.

Last question, do the symptoms I am experiencing can also be caused by low compression? Runs great and normal when the car is cold but if you drive it for a while it loses power?

BigCajun

iTrader: (1)

I think you'd notice hot start issues before performance problems if you had real bad compression.
Get your OBD scanned, that will help narrow down the misfires.
If you're able, drop that cat ASAP and inspect it.
I'd avoid driving it if possible until you figure it out, unless you have your old cat to gut or a midpipe.
Misfires kill cats, bad cats kill engines.

UnknownJinX

It's all guesswork until you drop the cat and inspect it.

Tackle problems one at a time.

Dude_Trust_Me

PROBLEM SOLVED!

Hi everyone, just wanted to update this post in case someone has the same problem:

I inspected the cat and the honeycomb seemed intact. So that was not the problem. So I saw that my drive belt was split in half! Replaced it and the problem persisted...

Finally, I saw so many posts advising to clean the MAF sensor. I was skeptical since I would NEVER believe that a MAF sensor could cause extreme power loss and stalling. Boy I was WRONG! The sensor was very dirty and had oil in it. So I sprayed it down generously with a MAF sensor cleaner and reinstalled it.

Voila! Problem solved! The car even idles great and accelerates like I've never seen before.

UnknownJinX

Glad, you got this sorted out.

This brings up one question, though: what kind of intake are you using? Over-oiled K&N is notorious for this.

Did you give the intake duct and the throttle body a quick wipe as well?

Lastly, I am still curious to see how long the Magnaflow cat lasts under the rotary exhaust heat.

Dude_Trust_Me

It's the original intake. Actually the intake duct had oil in it as well and I wiped everything off. I'm not sure how oil got in there. The throttle body was clean.

Since I was previously convinced that it was the cat, I ended up ordering a TurboXS highflow cat. Also, when I inspected the cat, the previous owner actually welded it into the midpipe and even welded the O2 sensor into the cat! The welding was done so poorly that it has cracks and it's almost falling apart. So needless to say, I will be replacing the cat.

NotAPreppie

A small amount of oil residue in the intake track is normal oil mist from the breather hoses.
Pools of oil in the accordion tube or oil stains on the air filter usually mean overfilled oil or bad side seals.

BigCajun

iTrader: (1)

That's good news, thanks for the update.

Before you install your new cat, be sure to get your OBD scan to be certain you have no other issues.
You don't want to ruin your brand new cat.