I did an unconventional experiment when I accidentally broke my exhaust nuts & couldn't screw the pipe on. This led me to drive 360 miles without a midpipe, cat & muffler.
The result was the best gas mileage ever. I drove 330 miles before the gas light came on. My previous best was 315.
I put on a highflow cat but took it off because it had a severe drop in mileage. But when I take the whole thing off my mileage goes up..hmm so now its time to tamper with the 2nd O2 sensor.
Its something I don't want to duplicate again but it led me to do to 2 different tests to try out. The problem with my car is if u lean the fuel too much the 2nd O2 sensor picks it up because theres no gas to burn in the cat. Its all got burned in the more efficient A/F ratio. The 2nd sensor mimics the first sensor & inefficient CAT cel (p0420) is given robbing mileage again
If you take the whole thing off the second O2 sensor will pick that up too. So how does leaning out the engine throw a check code but not having the exhaust on at all doesn't?
KYLE!!!! I didn't know you were on here too. What's up buddy?
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
Check engine light came on less but it still appeared a few times. Around The same mileage too but the A/F ratio was sticking longer. It wasn't re adjusting to 14.7 levels except around the times the CEL coming on.
last test is the O2 Sensor defouler. O2 Sensor Simulator & Efie are off the rear plug again. Lets see how it go