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LTFT = -14% in Both Banks STFT = +/_ 0.8-2% at 96°C (Operational Temp)
My car has no codes but the LTFTs have persisted for about 1 month now and plenty of driving cycles.
There are no loss of power issues as I drive.
The MAF sensor is new. I would appreciate a troubleshooting routine to test the injectors. I've had the car for 10 years and the injectors have never been changed. However, when I turn on the engine in rhe morning, it starts rapidly without any hesitance or rough idle.
Since the LTFT is the same -14% on both banks, its unlikely an injector issue as unlikely that two injectors, on one each bank would go bad at the same time.
You mention the MAF is new; was this replaced before or after you noticed the negative LTFT. If before, then I wonder if the new MAF is bad. Please let us know the timing of when the MAF was replaced.
The negative LTFT indicates the engine is try to run too rich.
I would suggest checking fuel pressure; I had a similar issue after the fuel pressure regulator failed.
The Check Engine Light is ON. Car runs well under all loads.
Today, the left LTFT is -10.9% and the right LTFT is - 12.5%. So, leaking injectors might be an issue. I have never replace them (64K miles). My car has no fuel reg; the filter structure itself provides the suitable pressure on the basis of RPM. I bought a fuel rail pressure gauge to measure the fuel rail presssure at the sampling port.
I am considering refurbushing the ones I have with a kit ebay sells vs bying new ones.
PreCar STFT are at +/- 2% in both banks.
Also, I usually by Bosh O2 sensors, but my local EuroCar parts sellers sells post Cat NTK O2 sensors for $138 each. Are these sensors reliable?
Thanks!!!
Your guidance is appreciated.
Cheers.
Last edited by José Antonio P.; Jan 4, 2026 at 05:33 PM.
It will be interesting to see what your fuel rail pressure is.
HOWEVER, unless I'm just not reading your posts correctly, did the negative LTFT start AFTER or BEFORE you replaced the MAF? If AFTER, then there is your problem - a bad or wrong MAF.
Other than replacing the tiny filters and the o-rings, I have never tried to rebuild an injector. You might also try cleaning them in an ultrasonic bath.
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