I keep getting the system running too lean code. Replaced cat, vacuum lines besides the bigger ones on the intake, replaced maf, replaced, coils, plugs, wires, seafoamed before replacing the cat. Still the same thing. Lately (2 weeks) at 4k rpm's it looses power if i push it too hard, if i keep pushing the rpm's shoot right up like normal with no hesitation, then smells funky from the hood, does not smell like exhaust or electrical burning. If I floor it from 1st or 2nd gear, the engine light flashes indicating obvious misfire in progress, and sometimes it idles up and down for a min or 2 at a light and then dies. But starts quickly right back up and runs normal. I also notice that while the car is still cold and warming up, the idle is perfect with no problems, when it gets to 170-190F, I can hear the engine start to make small shutters and hear small backfires in the exhaust. Weird thing is, on the interstate I can go well past 7k rpm's without a power problem and it drives normal. And the lean code has been on for 2 years now, and only this past 2 weeks has this power problem started. I think the car is saying "OK dude, if you keep ignoring my lean code I ill start giving you **** until you fix me" lol. I know this car in and out especially mechanically, but finding the problem is always the Bi***. Xmas left me broke so no repair shops for at least a month. Does anybody have any ideas? The only mod I have is a drop in (clean) K&N filter. Even bought a Mazda paper filter to try and still the same thing. I cannot figure out where this air leak would be. Could it be my smog pipe going into manifold? Or is that past the vacuum part of the engine? Any help is greatly appreciated.

Attached is the adobe pdf of the OBD2 scan data I did last night, from engine start to stop. Idling the entire time.

 

Faulty O2 sensor.

 

Which One would it be? Could you explain?

 

Downstream O2, it's where AFR are generated biased off of under closed loop tuning and reads AFR in open loop as well. A faulty sensor could throw this code, or could create a lean condition. Running lean for to long is highly damaging likely your engine has suffered.

I would get a compression test, would not be surprised if it fails.

 

i kind of agree with the 02 diagnosis.

the engine RPM and airflow are pretty steady, and the rear o2 is switching like it should, but the front 02 isn't moving.

here is the list from the FSM for P0171, O2 is on the list

• Front HO2S malfunction
• Excess air suction in intake-air system
• Leakage exhaust gas
• MAF sensor malfunction
• Fuel line pressure malfunction
• Fuel pump unit malfunction
• Leakage fuel
• Ignition system malfunction
– High-tension lead malfunction
– Incorrect power supply to ignition coil
– Ignition coil malfunction
• Insufficient compression
– Metering oil pump malfunction
– Engine oil condition malfunction
– Rised oil pressure
– Oil passage malfunction
– Engine malfunction
• Fuel injector malfunction
• PCM malfunction

 

OP should have worked on this when it first started happening. Not through random components on it hoping to fix the issue.

Again would not be surprised at all if that engine and Cat are shot!

 

If the car has been running lean for 2 years it might be a good idea to get it compression tested before potentially wasting your time.

 

Might want to fix the lean problem first so you don't ruin the next engine as well.

 

I bought a used o2 sensor from a guy in new jersey on eBay, Its a good and bad thing. the lean code is not even pending after 5 warm ups and starts. But...... The sensor has a code of its own, p0031, heater circuit too low. But the lean code is gone and nothing else but the heater circuit too low code is there now. One thing that is aggravating the nuts out of me, now the car starts missing immediately when I start it and not after it warms up, its hard for me to tell if its missing or if the exhaust is backfiring, because I hear the popping in the exhaust. I'm starting to think the cat-back is clogged from the old converter, those pieces had to have gone somewhere when they melted, I doubt they liquefied and dissipated into thin air. At least I know the lean code was that 02 sensor and nothing else major. I'll just get my money back for that sensor, buy a new one and call that code gone. Hopefully the acceleration at 5k rpm is solved too.

 

The heater code is probably for the o2 sensor heating element. It needs to be up to temp before it starts reading correctly. This explains why it's not a problem when warm. At least you seem to have confirmed that the issues are with the 02 sensor and not leaky gaskets, etc. From here, either buy another sensor if this code is bugging you or try re-installing the original sensor - could be that it wasn't mounted correctly the first time around, which could result in a lean reading.

 

Seriously, you can pick one up for 100 bucks at autozone why would you buy one second hand.

Might as well perform diagnostic work with uncalibrated equipment, thats basically what you are doing. I can't wrap my head around your thinking process, not only have you been consensually neglectfully damaging your engine for two years when you do decide to try to fix it, you fail miserably by trying to cheap out.

Now do it again, only do it right

 

So, the guy i bought the used sensor off of kindly sent me a replacement sensor but its throwing the same code. Could that be coincidence or is is more phesable to say that the wiring on my harness side is doing it? I'm 50/50, because the sensor that had the too lean code did not have the heater circuit code, and the replacement sensors that have the heater code, does not have the too lean code. I will go ahead and buy both new sensors when I get the money next month, the idle is fixed and its not stalling, so that worry is at least gone. It misfires around 6k rpm, says multiple rotor misfire, they are new plugs, coils and wires, unless I bought bad ones, i can phase that out, could the exhaust after the cat be clogged? My compression test done on the engine came back good so thats out too. It just stumps me on why it misfires when revv it too high. Still a popping sound coming from the exhaust too at idle. Eh, if I diddnt love this car so much, she would be soon having a date with a match and lighter fluid.

 

A thought on the lean code. The computer thinks it is running lean, right.. And it cannot adjust for it anymore so it screams for help and sets the CEL. In the process, it is dumping every bit of fuel it can in to correct the lean code, Right? That means it has been running incredibly rich for 2 years, not lean. Right?

If that is the case, (comments please), then once it is running you will need to deal with that, likely with the CAT.

A suggestion is to do the 20 brake stomp resent, especially if you have changed the sensors for something that works... Then be ready for it to re-learn...

 

If that was the case then it would be a PCM or a sensor fault, if the car is actually running rich but reading lean their is no other component that would cause that.

Which means replacing the O2 and still getting that code means you have a PCM problem, the only way to confirm this is to go to a race shop and have them hookup their wideband to compare. If both read lean than you are in-fact lean, which could be anything on the fuel side that is failing.

 

when the Long Term Fuel Trim; LTFT exceeds +20% it will turn on the CEL for this code. the ECU will keep increasing the LTFT, after the light comes on.

the ECU has a set of AFR targets, and if its default output (rpm x airflow) is leaner than the target, it adds fuel.

the ECU is allowed about 20% correction just for variations in engine health/tuneup/and to an extent accelerations, so its actually supposed to move around a little.

 

UPDATE....

The other used sensor would say oxygen sensor heater circuit low. I replaced it with a brand new NGK Sensor and now the lean code is coming back. And before I started the car up the first time, i did the 20 brake stomp to reset the computer. I am just stumped on this. I guess the only way to fix this problem is to bring it in for a week, spend a million dollars on it and just ait another 6 months for something else to go wrong. Hate to say it, but I am not an rx8 fan for quality anymore. Looks good, but that's it. Any other suggestions? If I get another graph like I attached before for the stats of the car live, would that help any now that the new sensor is in? Let me know and I will get that put in here asap.

 

Check the fuel pressure. Could be blocked injectors, lines, filter or the pump giving out when warmed up.

 

Buy an OEM front sensor from Mazmart and quit pissing with cheap ones. That will rule that out. Then systematically start looking for issues. Dont just throw parts at it. What are the fuel trims at other than idle rpms? The most common reason for lean codes is a small vac leak. That will show high trims at idle..but normal everywhere else

 

Im actually starting to think it could be the fuel pump. It was doing that misfire before when I replaced the fuel pump when I first got the car and the new one fixed the problem. And that was a new oem part..... I dont buy oem unless its necessary, im not paying 10 arms and 5 legs for a part that is just as good as others. So im not (pissing) money away...

 

Here are the obd reports

 

Last one.