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I got my 8 on Monday, and it’s been great until yesterday. I went to start it in the morning to make a store run, I let it warm up as usual, but as soon as I left my driveway, it wouldn’t go over 3000rpm or about 12mph. The previous day, I got a check engine light for a p0171 (bank 1 lean) code. I cleaned the MAF sensor, cleared the code and the CEL turned off and stayed off. The first thing I did after the car seemingly went into limp mode was check the MAF connection but that seemed solid. After checking the sensor connection, I checked the fuel trim, which was a staggering 21.9% at idle. I checked for vacuum leaks, but nothing. I did some research online and found people who have had similar issues due to the OMP position sensor failing, but I don’t know how that would affect fueling. The car has 110k miles on it, and I am unsure of any engine rebuilds it has had if any (the car was free with a clean title, I didn’t bother to check). Also, the engine cold starts and warm starts perfectly. Any help would be appreciated.
Front O2 sensor is likely faulty and needs to be replaced. That’s what it was for me once. Similar symptoms too. If it’s not that it could be OMP related as it can cause a limp mode scenario. Think more likely the front O2 sensor is the issue since you mentioned wild fuel trims.
The 3000 rpm thing is typically related to the OMP. If it was overfueling there wouldn't really be a clean cutoff, it would just be miserable in all rpm ranges. Possible a rodent got under the car and went to town on wiring and vacuum lines? The OMP is pretty low to the ground.
The 3000 rpm thing is typically related to the OMP. If it was overfueling there wouldn't really be a clean cutoff, it would just be miserable in all rpm ranges. Possible a rodent got under the car and went to town on wiring and vacuum lines? The OMP is pretty low to the ground.
True, definitely worth checking OMP as wires could be damaged or water could have gotten into it. Front O2 sensor possible issue as well.
It's not really a clean cutoff, it's more like the car is only making like 30hp. I could barely get it up my driveway. Also, the idle feels not as smooth as it should be. I'm not sure this info will help at all but I hope it does. From the looking I've done, the omp position sensor seems to be identical to the tps on a suzuki xl-7, and a chevy tracker, so I may grab one from a scrap yard and give it a shot. Edit: The check engine light has turned on, but there are no codes.
Last edited by Dahtemba; Jan 2, 2021 at 11:14 AM.
Reason: addl. info.
There is a code but it's not readable by your reader. This typically means it's an OMP code, specific to Mazda. Not every reader understands. If you're using your phone as a reader, see if you can get the Mazda manufacturer specific code library foe the app you're using.
I don't know about swapping in rando parts, but read about how to align the OMP when you do reinstall a replacement, or even just reseat yours.
There is a code but it's not readable by your reader. This typically means it's an OMP code, specific to Mazda. Not every reader understands. If you're using your phone as a reader, see if you can get the Mazda manufacturer specific code library foe the app you're using.
I don't know about swapping in rando parts, but read about how to align the OMP when you do reinstall a replacement, or even just reseat yours.
The A/F ratio is off by a lot. Not suggesting replacing, but swapping it if there is no issue with the OMP, though you are right, it is likely an issue as most limp mode scenarios are OMP related. That still shouldn't fudge the fuel trims though. That seems like an O2 sensor issue.
Last edited by CaymanRotary; Jan 2, 2021 at 04:25 PM.
Yeah, good point. Could be multiple issues, or something electrical common to all of them. What are the rpm, airflow g/sec, AFR and fuel trims (short and long) reading while fully warmed up and idling?
The rpm is at 800-900 when warm, but if you rev at all when cold (2000rpm max) it wants to die. the airflow is correct (around 4 g/s) and when warm and idling the STFT is 0% and the LTFT is around 20%. Also the car still starts flawlessly warm or cold.
The rpm is at 800-900 when warm, but if you rev at all when cold (2000rpm max) it wants to die. the airflow is correct (around 4 g/s) and when warm and idling the STFT is 0% and the LTFT is around 20%. Also the car still starts flawlessly warm or cold.
4g/s is too low. Nominal for 800rpm is around 5.2g/sec. Add 20% to your 4g/s and youre close, which matches your almost maxed out LTFT. Vacuum leak.
Hey
I have a 2004 Mazda RX8, Manual 6spd
I seem to be having a limp mode issue, I have had the car stored for 5 years.
I replaced the plugs, spark plug cables and coils with BHR coils, I also replaced the front and rear O2 sensors.
When I start the car it will rev to 10k but after a couple seconds the computer seems to be putting it into limp mode. Not allowing the car to rev past 5k rpm. Even though its at operating temperature.
When I check the error codes it comes up with no error codes, but the engine light is on.
The car will "hot start" instantly no issues starting.
I Can replicate the same issue every time. If I shut the key off for a couple seconds and then fire it back up, it will rev to 10k rpm for a second or two but then it returns to limp mode; limiting it to 5k rpm again.
Need help please 🥺
Im thinking it possibly could be a weak fuel pump? But shouldn't it throw a an error code for a dying fuel pump? Also why will it rev to 10k when I first fire it up if the pump is weak?
