Well, the inevitable finally happened today to my beloved '04 RX8 with over 120k miles...

Started car cold in mid-40dg weather, and drove about 2mi with surging/stuttering/CEL flashing intermittently for about 2mi. Saw spark flying out of exhaust or from back of car and had burning smell inside the car, so pulled over and shut down the engine right away. Saw catalytic converter's O2/AF sensor glowing red, so figured it's plugged/obstructed.

Went back to the car later on with tow vehicle (pickup truck) and recovery/tow strap that is spec'd well over safety limit (working strength ~7k lbs and breaking 20k lbs and 4in wide). Unfortunately, it was my first time using such a strap, and I made an operator error of threading through the square openings on the hitch itself and doubling back to the towing eyelet bar (to reduce the 30ft length), rather than the drawbar/ball with the reinforced strap eyelet ends. The strap snapped/sheared as the result after some distance. Due to slightly blocking the road, I had to start the car out of desperation and pulled into the adjacent parking lot (short distance possibly flooding engine). Got a stern talking from LEO and let off with a warning in the drizzle, but that's another story.

A couple hours later, I decided to go back to the RX8 after getting multiple $100 quotes for 2mi towing back home (on top of $50 allowance paid for by credit card's roadside assistance) and tried starting. It cranked and sounded weak without ignition catching on, so put battery jumper pack on it, and heard exhaust backfiring twice while almost catching but not quite.

Current MIL codes are unknown, but had P0302 (cylinder 2 misfired) & P0300 (random/multiple cylinder misfire detected) about 2mo ago with similar surging/power loss but without smoke/glowing cat. Car was mostly fine since then until today's total meltdown, other than occasional stuttering in first gear upon cold start.

TLDR: Exhaust shooting spark and trouble starting with backfiring , P0302 and P0300 possibly. Catalytic converter glowing red, especially the O2 sensor location after engine is warm
So here I am pondering the following choices:

1. Tow back home on a flat bed (2mi) with family's AAA Plus, and changing the catalytic converter (got a spare one from years ago), and hope for the best. And maybe tow it a second time to shop if not working still.
2. Tow to independent not rotary-specialty shop to get diagnosis. I'm nearby Berkeley CA.
3. Junk the car and have it towed away by not-for-profit for donation (maybe apex seals were goners)

Our picturesque town is overrun with LEO, so probably not gonna try towing it home with my truck again, even with proper strap hook-up.

Your opinions/thoughts are appreciated!

 

Start by getting rid of the cat with a cat delete pipe, replace all ignition coils, all wires, and all 4 plugs with the appropriate replacement parts. Also, buy a compression test tool and check that engine compression.

 

If the car didn't have this problem what would you do with it? Did you plan to keep it longer? Because you could replace the cat and ignition and maybe the engine, but at that point is the price worth it? You could buy another car for that cost.
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You could also try to sell it as a non-running shell, especially if it's in good shape otherwise.

 

if you have some sort of rental server near you (uhaul) a lot of times you can rent a car dolly or trailer for less than 50 bucks.

 

Look up tow dolly, and I guess disconnecting driveshaft would be necessary for RWD. Flat autotransport trailer would be better, but would need a winch to pull it into the trailer.

Going to enlist family member for AAA towing back home.

 

Going to bring it home to work on before giving up on it. It's my fun/autox car before kids showed up, so lots of sentimental values. Not gonna dump serious money to fix, such as engine rebuild.

 

Hahaha, California is probably not what you would call cat-delete-friendly...but points taken about doing the whole 9 yard thing again. Still had original cat, so that's probably the 1st thing to try to replace.

 

Dude i live in bakersfield, local law enforcement around here is pretty strict about carb stuff, especially if you are driving anywhere close to where a car meet is happening. Ive seen cars get raised up on jacks for inspections in the middle of car meets after a local PD drove through and the guys hood was open. Its strict here.

remove the cat for testing and diagnosing the issue, after all issues are resolved and you decide to keep the car, install a replacement catalytic

 

Got it. Replied on mobile, so didn't see your location on the sidebar.

 

Got the car home with AAA, so will update again when I sort out the issue; after starting up the NB Miata after 2~3 years of storage and gas furnace limit switch error issue.

Thanks everyone!

 

every two years this gem "gas furnace limit switch" crops up on my old 1970's boiler. I buy them in pairs.....

 

Exactly this. Would have been easy to do a basic compression test with a regular compression tester (getting total psi on each chamber plus hearing pulses on the other). If all was okay you could have removed the cat started the car to see that it ran okay. If it did you could have knocked out all of the clogged material reinstalled and enjoyed a nice horsepower increase. Install a new cat when you need it.