Troubleshooting Sequence
 

Noob here, I just bought one of these beautiful cars, but wouldn't you know it came with engine troubles. Imagine that.It is a 2004 model with 76k miles and has the automatic transmission. I have read at least 30 threads and although many people seem to have very similar issues, I haven't been confident that anyone has an exact match for my particular issue.

As I said, I have looked at dozens of these threads and other sources as well, and it looks like it could be coil packs, spark plugs, plug wires, back cat, vacuum leak(s), various air/fuel ratio sensors related or, heaven forbid, a blown engine. I was hoping to get opinions on what some more experienced rx8 owners think. Also, in what order would you troubleshoot?

1. Car will absolutely not start when warm.
2. Severe lack of power until up to 4k rpms.
3. Idles rough but somewhat steady @ a little under 1k rpms but not as badly as some I've read about here.
4. Check engine light has been on since I bought it a couple of weeks ago. 2 codes were given: both were P0300, multiple misfires detected.
5. Brand new K&M intake
6. Alleged new coil packs (will be looking here first just to confirm this)

6. When I first bought the car, I drove "pretty aggressively" on the interstate on the way home. I got it up to about 90 @ about 6k rpms before it stopped accelerating and the check engine light started flashing . It didn't die or anything, but it just seemed to have not let me go any faster but would maintain that speed.

I am somewhat handy with turning wrenches and am going to do my very best to DIY this thing, but I have several questions and any other insight you guys might have. Is there a more relevant thread I missed? In what order would you try to diagnose the issue? If I drilled a hole through the back cat with a drill bit on a long, flexible extension, would it fix the issue if it's the back cat? And if I did drill it, exactly how much louder would the exhaust be?

I appreciate anything you guys contribute to this thread. Although I have always loved these cars, I l didn't want to get it undrler the circumstances in which I got it. But I have a family and they have to go places. Also, even though I hastily purchased my car, it doesn't mean I can't make it the nicest car I've ever had.

Hard starting when warmed up is a very very common symptom of low compression.

Book it in with Mazda for a compression test. Very few local mechanics have the specialised compressor tester required to calculate the rotary outputs.

Thank you for your reply. Are you familiar with/trust the accuracy of using a standard compression tester, videoing the test, and slowing it down?

You can't use a conventional compression tester on a rotary engine, hence why I recommended Mazda.

Compression
 

Hypothetically, if I do not meet the threshold in the compression test, does the motor need completely rebuilt/replaced?

Not necessarily, if there is a build up of carbon ( which is common ), causing lack of compression, it's possible for a hydro cleaning process to clean the apex seals.

The rotary engine is a specialised engine, very different from a conventional piston engine, which requires specialised tools, knowledge, servicing and repairs.