06 RX8, New Engine, Car turns off on idle

Outcome? Solution?

Was this issue ever solved? I'm having this exact same problem. Just had a brand new engine installed and the stalling at idle issue started. sometimes it revs 'hunts' up and down between 700rpm~1200rpm until it finally stalls out when idling. The dealership couldn't find an issue. No fault codes on ECU. Engine shows good compression and no vacuum leaks. The Gas pump was tested and gas pressure is good. The ECU was upgraded and reloaded with new maps. All driving history was cleared, ESS was reset and VRAM cleared. The car was driven for new mapping until it completed all cycles. Voltage regulator shows good output. I have replaced the MAF, spark plugs, wires, Coils, ECU/PCM adn the air sensor in air intake. The shop is telling me they are going to have to rebuild the "Brand new" engine to see if something was overlooked at my expense with no guarantees.

Hey, wondering if you got this issue figured out? I have pretty much the same exact problem! I've read countless threads and similar issues but your situation seems like the closest match to mine. New engine, replaced coils, wires, plugs, O2 sensor, MAF sensor, air filter in stock airbox, gutted cat, cleaned throttle body, no vacuum leaks, cleared RAM/ESS, did re-learn process, etc. The car started doing this before I took it in and got a new engine and its still the same. It pulls harder because its a new engine but the hunting idle and stalling is still the same, maybe even worse...IM STUMPED. Any help or additional things you have tried would be great, I love my car but this issue is so frustrating.
 
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Udate: Follow-up to my own question...

Hey, wondering if you got this issue figured out? I have pretty much the same exact problem! I've read countless threads and similar issues but your situation seems like the closest match to mine. New engine, replaced coils, wires, plugs, O2 sensor, MAF sensor, air filter in stock airbox, gutted cat, cleaned throttle body, no vacuum leaks, cleared RAM/ESS, did re-learn process, etc. The car started doing this before I took it in and got a new engine and its still the same. It pulls harder because its a new engine but the hunting idle and stalling is still the same, maybe even worse...IM STUMPED. Any help or additional things you have tried would be great, I love my car but this issue is so frustrating.

Update: So today the last two things I did, after all of the above mentioned parts were replaced, was gut the cat and put in a new O2 sensor. I was afraid it didn't work but after about an hour of driving the ECU started to learn everything again. It started out with a hunting idle and random misfire code approaching redline...but I drove about 110 miles today with multiple drive cycles and now it runs like new! The gutted cat didn't noticeably increase the sound inside or out accept at higher RPM, no CEL, and idles much better. I had a spark plug anti-foul spacer all ready to go if I got the O2 CEL but I never did. I have heard the earlier models may not need it if you gut the cat but I wasn't sure.

*Important note: I had replaced the O2 sensor less than 1,000 miles ago with a cheap one on e-bay for $35. IT FAILED and the car had a FIT with a bad O2 sensor. I had it tested to be sure. I have read a million posts with people replacing things like I did but one thing that everyone seems to NOT want to do is the O2 sensor because a nice Bosch is $160. I finally coughed up the cash and it fixed my problem...plus there's a year warrantee on the Bosch. A good thing though is the bad O2 sensor caused me to take it to the dealer for a compression test, it failed, and I got a brand new engine out of it!
 
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