So I recently purchased a 07 IS250 rwd, as a gift to myself for my birthday. I plan to build it and use it as a DD with some possible track days. But for now its a DD. Anyway it has 200k miles on it, still runs and drives smooth no issues besides needing a new rotor, brakes, simple things. Ive already put about 1200miles on it. About 150 miles in the check engine light, vsc, trac off trifecta lit up my dash. I had it scanned and codes P0171 Too Lean Bank 1 and P0174 Too Lean Bank 2 were thrown. Ive already replaced both upstream O2 sensors with Denso brand sensors making sure not to get any anti seize on the probe and using dielectric grease at the connections, there was a small dab of anti seize that smeared on one of the probes but I used gloved hands and a microfiber towel to wipe it off. After installing the sensors the code cleared itself considering i removed the battery, but now theyre back on, showing the exact same codes. i cleared it again and they have returned once more. whats my next move? does the ecu need time to read the new sensors? car is currently running rich btw.
More history. The lights cut on when i first got the car due to me not tightening the gas cap lol they cut off shortly afterwards then randomly one day they returned and would cut on and off periodically. I noticed they seemed to cut off when I would drive more aggressively accelerating harder etc or when i had more weight in the car as i was in the process of moving which is the primary cause for the miles, and why i mention the weight in the cabin/truck. They would cut on when i drove more relaxed, also I can smell the excess gas its a sulfur/eggy type odor ill smell periodically as i drive, any one else fix this issue? i would love to know

 

also getting poor fuel mileage

 

Any intake modifications other than OEM piping? Do you have any live data to post of the fuel trims?

 

Perhaps there is a crack/leak in your exhaust systems causing air to enter the system and causing mis-readings by the O2 sensors, thus throwing the codes?

 

no intake mods but could upgrade the air filter to the k&n, the oem one is still in place it is new but still the oem filter =(
and no live data, what device would i need to read that i can always upload pics and videos

 

possibly ill put the car in the air and take a look.

 

so i was doing some more reading on the forums and decided to replace the gas cap, bought a new one from auto zone for under $15 USD.
popped it in and started the car and the lights shut off instantly.
drove for about 50 miles over a day grocery shopping running errands etc and the lights illuminated once more.
so im thinking that im getting air into my fuel line somehow.
considering im not leaking fuel im wondering if the fuel pump is going bad
any thoughts?

 

thinking critically perhaps theres a leak in the exhaust manifold, before the upstream 02 sensors allowing excess air into the exhaust which would trip the sensor into believing the engine is running lean, ecu compensates by running rich.