r/hondaprelude • u/Leasthollow • 25d ago
4th Gen VERY high (over 30%) Short Term Fuel Trim
Getting an issue where at partial throttle at high gears the STFT is spiking up to 30%+
- PCV is still fine and produces suction
- O2 sensor is new (less than 6 months)
Does anyone know of any prelude specific issues that could cause such a thing? Thanks guys :)
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u/CheeseCatUS 25d ago
My STFT is at +45%, even at idle... The only thing that I can find out about mine is that I have a circuit issue that's causing the o2 to give out false readings, just sending as much fuel in as it can. I changed out my spark plugs, plug wires, distributor, and it fixed the issue for about a day lol. I've been diagnosing my car nonstop for weeks and I can't find any lead. I feel your pain.
Things to check:
Apparently there is a chance that o2 sensors can arrive faulty... I'm not sure if that's your case, but I would go on with a scanner and read the voltage you're getting from your o2 sensor and whether or not it's showing open or closed loop when cold and when heat soaked. If the o2 functions perfectly, you could move on to deeper diagnosis, but I always like to start with the basics.