Ran the car a little hard last night and noticed that the bung for the rear o2 sensor was glowing.

I’ve seen all of the posts that a glowing cat indicates a failed cat. Does that rule apply in this situation?

 

Yes. It's never a great sign. Take the cat down and inspect it, and make sure your ignition is fresh so it doesn't kill the next cat.

 

thank you. The ignition system is less than 6k miles old (hitachi coils). I’m punching the cat out tonight.

 

Well wait, don't punch it out. It's worth a lot if it's still in one piece. Examine it, see what's going on. You can always sell the cat and buy a midpipe.

 

The cat was bad and was breaking apart inside. So we punched it out. It didn’t make a difference with the misfire issue, other than picking up some top end.

We’re getting a misfire notification at high RPM. Can’t feel the misfire if the throttle is at 100%, but if throttle is around 25% we can feel the misfire.

We replaced the following parts so far.
- Spark plugs (they are gapped properly)
- Ignition Coils. They are about 6000 miles old and we swapped them around this morning to see if the misfire would change from rotor 2 to rotor 1. There was no change
- Plug wires
- Cleaned the MAF
- reinstalled the factory airbox
- punched the cat out
- All rotor faces have 106-108 at 267rpm, about 30 ft above sea level.

I ordered a new front 02 sensor and will check/clean the ESS next, but looking for ideas on other things to check.

I pulled the attached logs with an OBD2 scanner.

 

installed the new o2 sensor. There’s a notable difference in how well the car runs at high RPM, and there’s a change in the misfire.

It now misfires primarily under a low throttle input at mid-range RPM. Going to start a search for vacuum leaks now.

I've attached a log with the car actively reporting a misfire.

 

Log at idle

 

You have a high long-term fuel trim and low airflow for an 800 rpm idle, which indicates a vacuum leak. Can't tell you where it is, but there is one. What intake do you have?

 

It’s the factory intake with the usual mods.

Thank you for your feedback. I sprayed the hoses yesterday with carb cleaner and didn’t get any feedback from that. I’ll hunt down a smoke machine or a vacuum tester

 

What are the usual mods? An easy to miss one is the VFAD nipple under the throttle body, out of sight

 

This was done: https://www.rx8club.com/series-i-do-...ke-box-130332/ before we purchased the car as well as removing the variable part of the intake path.

 

Yep so if the VFAD has been removed, you'll want to make sure its vacuum line is capped.

 

One failed cat here also, the first section of the cat deteriorates and blocks the flow in general resulted in excessive heat in midpipe.
Replaced ignition coils for good measure. I had one time too much oil filled to engine which flooded the intake and rotors with the oil. Now filling only to max half way the dipstick.