Corolla gives me a P0170 code

Question

I had an issue when sometimes my 2000 1.8L Corolla stalls if I roll in reverse. A few weeks later, I got a check engine code pointing to Bank 1 Sensor 1 as an issue. I replaced it, cleared the codes and thought it was cured.

A few weeks later, the light came back with a new set of codes pointing to the MAF sensor. Aside from a barely perceptible vibration at idle, it drove and continues to drive fine. I cleaned the MAF sensor and the check engine light disappeared. Again, I assumed the problem was cured.

Today, the check engine light comes back on with the same code. I am wondering whether there's a leak in the system. Perhaps, the 02 sensor isn't snug enough on the exhaust? I've included the freeze frame for the code, I also included MAF volume vs the 02 sensor response (long term) graph when tapping the gas while in park. The last images are two pages of sensor data while holding the RPM.

Answer 1

LTFT at 29.7% seems mighty high. I'd start by looking for unmetered air leaks aka "vacuum" leaks.

Unmetered air might be fooling the primary O2 sensor - so called "false lean". Easy to check and a standard part of my KISS rule/Occam's Razor mantra.

Interesting about the "reverse" stalling comment. My spidey sense says to check any rubber or plastic intake hoses after the air metering for cracks or splits, especially any flexible "accordion" sections. What I have seen many times is that such a split is mostly closed, but still causes an unmetered air leak, which eventually leads to high LTFT and poor running and fuel efficiency.

However, reversing causes the engine to torque over in a different way, and potentially opens up that crack very wide ... creating huge bucking or stalling. This is from the airbox being mounted to the car, and yet the intake hose mounted to the intake - possibly compounded by weak engine/transmission mounts.