So I've got a problem and please forgive me if I provide too much information.

During cold start the engine is running open loop as it warms up, RPM transitions from 1700 to 1300. At that point it switches to closed loop and continues to lower idle. During this time the O2 sensor is reading about 0.8V and the STFT is -15% to -20%. Once RPM hits 1100 the engine dies like fuel is cut off and STFT spikes to -25%.

On restart it starts in open loop again and holds at 1100 RPM while O2 sensor reads about 0.9V. As soon as it switches to closed loop it dies.

Restart again, I hold the RPM at 2500. Once it switches to closed loop the O2 and STFT are jumping all over the place. STFT is always -XX%. It holds RPM despite the fluctuations. I rev and hold at 4500 RPM and O2 and STFT hold steady at about 0.8V and -15% for about 30s then start to fluctuate wildly. It holds RPM despite this until coolant temp reaches 100*C then it dies like before, like the fuel is shut off (not sure if coolant temp is relevant just happened at that time). The only error code I'm getting is P2004 which doesn't seem relevant.

Background: 2005, 105k miles. I have just rebuilt the engine (well, second rebuild because I didn't replace the rotor seals with previous rebuild because I was cheap, so had to rebuild again).
List of parts replaced: All rotor seals except oil scraper rings (they showed almost no wear), both rotor housings (some chipping on the edges of old one), gear and rotor bearings, oil lines with SS braided, radiator (I broke off that plastic nipple on top), made some new OMP oil lines, added Sohn adapter, BHR coils, NGK spark plugs, oil catch can (disconnected right now to eliminate possible causes for problem), and obviously all gaskets and rubber seals.

After the rebuild it was running and driving but kept dying when it went to idle, it always started up again without a problem. I put probably 50 miles on it. I later figured out that it was running open loop that whole time because my O2 sensor was bad (low voltage error code). I replaced the O2 sensor with NTK part #25673 which I'm pretty sure is OEM and have my current problem.

Troubleshooting: I've searched for vacuum leaks by spraying starting fluid around the vacuum hoses and tested the valves and hoses with a vacuum pump, nothing noticeable. While running vacuum holds at about 18.5 in/Hg with very minor fluctuations. The air pump was working before I changed the O2 sensor but I don't think it is any more; I still hear a slight whine like it is being powered but it isn't very loud. No error code from it. I cleaned the MAF sensor the first time I took the car apart, and typical readings are just under 5 g/s at idle. I've reset the NVRAM and KAM using the odometer button and brake stomp.

Ok, that is enough for now. Thanks in advance for any help.

 

I'm not going to claim to be an expert on this, but I will refer you to a thread with a similar issue:

https://www.rx8club.com/series-i-tro...-trims-242769/

Since you recently did a rebuild, it's possible you're in the same boat as the OP of that thread.

 

Thanks man, I hadn't seen that thread and the problem did seem very similar. He seemed to be going kind of crazy with his mapping. His problem was mis-wiring his fuel injectors, probably because he re-wrapped his wiring harness. I'm 99% sure my wiring is correct; there is really only one injector each wire will go to and all of them fit. I guess I'll add my fuel injectors to the checklist though since they have 100k miles on them. It's just a pain in the **** taking the UIM on and off.

 

Have you performed a health check and noticed any pending codes? What history codes are stored?

 

Check you injector wiring. Had a similar issue with fuel trims being that far in the negative range after rebuild. Problem was had two injector wires swaped.

 

Sounds like you might need to smoke test it to verify the lack of a vacuum leak.

But yah, check your injector wiring one more time, as well.

 

The injector wiring is really easy to wire wrong...check it with the wire colors to be super sure.

 

Thanks guys for pushing the injector wiring, it made me check it with the diagrams and I did indeed have them wrong. I suppose I thought a little too highly of myself and how "I could never mess up something so simple." I will now revoke any bragging privileges I have acquired in my life and live a humble existence from now on. At least my baby is driving again though. Thanks again.

 

Glad you found the issue and after reading this thread and the replies, I believe that I've learned something very useful as well.