Alright, so I've lurked here for awhile and upon any other problem I've had before I've come to RX-8 club to find the info.

I've searched around through the stickies and searched through the threads with no sure luck.

First, my stats:
-2004 RX-8 with 130k miles.
-I've had the car since 2008.
-I have replaced the clutch master cylinder and my clutch due to the weld breaking.
-I have had no modifications done to the car, no kits.
-The last time I had an oil change at 125k miles, I also had my coolant refilled/changed. My transmission fluid was last changed around 110k miles.
-I'm not a mechanic by any means, just a DIY guy when something breaks.
-I'm based in Huntsville, AL.

Here's my story:
-I initially attempted to start it from a cold start but after not starting I backed off as it was irregular.
-I attempted to start it again with better luck. The moment it started a low rumble started to occur with the CEL blinking and my revs weren't getting above 2k~3k without giving it more gas.
-I turned it off, checked for any odd smells under the hood (there weren't any), and then pushed my car to another parking lot.
-I attempted to start the RX-8 again and drive it. The rumbling was still happening as if the car was shaking, I got it to a max of 5k~6k RPMs.
-I tried to let it idle, and it shut itself off.
-I tried to start it multiple times, every 1 out of 7~8 times the car would start.
-After getting it started I attempted to drive it around the parking lot and after 10 minutes the car was smoking. The exhaust system (The exhaust "cylinder" found on the underside of the RX-8 towards the very rear) was overheated glowing red.

So my question is what's going on? I thought it was the spark plugs causing issues, but if it's overheating like that once starting I doubt it's the plugs or the wires. I checked the coil or vacuum hoses on the engine and didn't see any damage before driving.

Could it be a misfire? I've looked through https://www.rx8club.com/series-i-tech-garage-22/suffering-misfire-start-here-222280/. If it is then what could be the cause? Low compression? I've looked for low compression symptoms and videos and none seem to have the same conditions that I have when starting. Maybe I'm missing a concept I don't quite understand about misfires?

I really don't want to end up junking the car, I don't mind the DIY but it seems like this problem will be the end of my RX-8's life.

RX-8 Club, thanks for any info on my problem.

 

Sounds like a clogged cat converter. If it is glowing red it is bad. It will cause misfires and you need to gut it or replace as it will ruin your engine.

 

Thanks 9krpmrx8, I will look at it and compare to photos of an RX8 CAT tomorrow.

 

First off... HUGE kudos for giving such a detailed post. Often it is very frustrating trying to help others, when they don't give you enough information to even begin troubleshooting.

Second, I agree with 9k that you probably have a clogged catalytic converter. If it turns out that is indeed the case, be sure you troubleshoot the root cause before replacing it. Often, a misfire (dumping raw fuel into the cat) is what causes the it to fail.

If it were me, I'd go ahead and replace the plugs/wires/coils at the same time... Unless you are absolutely sure they aren't an issue, and they are less than 30k old.

So, you are talking about the muffler... Near the rear bumper? If that's the case, I'm guessing the cat melted on the inside, the honeycomb came apart, and clogged the muffler. In which you will probably need more exhaust work than we originally predicted.

 

Thanks, I appreciate it. I just need all the help I could get with the problem.

So here's my update.

I removed the CAT, the middle exhaust pipe, and the exhaust muffler. Sure enough it appears that the heat was all happening inside the middle of the CAT. I also peeked into the muffler and found bits of something clogging it up.

So I have a question. I tried to start up the car with all this removed to see if it would even kick on. I had no luck, but it sounded better than before. Is it the RX8's security system not allowing me to start the car?

Here are my replacement plans over the week. I've got a stock catalytic converter and a stock muffler arriving Thursday. Monday and Tuesday I plan to replace spark plugs and the spark plug cables since I've already gotten my car lifted up. Thanks for that suggestion Wingznut. On Friday and Saturday I'm going to put the new parts in. Hopefully it all goes smoothly.

Do any of you have any recommendations for any replacement parts I may need to do as it's already lifted? Where is the best place to go to scrap my spare parts? Should I pawn the old CAT and muffler or take it to a few junkyards and get the best price for it?

Thanks for the help. Some pics are below.

 

Yep, a clogged cat can do some damage. If you were local I would have given you the stock exhaust set up, I have two in storage.

 

It looks like a plastic bag stuffed in your muffler?

 

Nah, those are chunks of the cat innards.

 

If you had no other issues, your engine should start and run (mostly) fine without the exhaust system attached. Perhaps you have a severe ignition issue, or maybe flooding from all the failed attempts at starting.

 

this exact problem happened to me at the beginning of the year.
i had zero problems with my car prior with zero modifications

turns out i had bad plugs and coils, which destroyed my cat.
i ended up getting plugs, coils and wires and a BHR midpipe

all i can say now is my car better than when i first bought it.

 

Alright a quick update. I don't know how to sage my post so sorry for the bump.

So I replaced my cat, my muffler, and my mid pipe. I replaced the ignition coils, spark plug wires, and spark plugs.

I started it up the first couple of times with no luck until I realized I had flooded the engine most likely.

I did the standard unflooding procedures and then tried to start up 10+ times until it stopped shooting smog out of the exhaust.

After that it started up fine, and idles better than ever.

My only problem now is that because I over heated the exhaust and burned out the cat I most likely burned out a wire. My engine check light is still on. My radio, console lights, and the inside lights won't come on. I can't get an engine error code reading. Luckily my headlights still work, as does the lights in the drivers dash so I can still see the normal readings for the car such as MPH, Oil, engine temp, etc.

I'll search the forums a bit for the problem.

 

What wires did you burn? i guess it's the o2 sensor if the cat was overheating...
Check the fuses behind the driver's door (mainly the "room" fuse), that's what generally causes the interior lights to stop working.

I would do a compression test, running with a clogged catalytic converter for an extended period of time could exacerbate engine wear.