Hi,

about a month ago, i added a fuel additive to the gas tank of my 2012 IS250 (@160K miles), refilled the gas tank until full, and parked the car til the next morning. In the next morning, i hit the start button, car started but then the rpms immediately plumetted to almost zero, but the engine recovered immediately and continued running, albeit roughly. Had a CEL; pulled the codes p0172 and p0175. On the climb-up out of the parking garage, the engine felt weak, and pressing the acceleration pedal didnt make it go fatser. After the car warmed up, it ran perfectly fine, but long term fuel trims were high (~ 10-15% on each bank). Took it to a dealership, and they said they couldnt find any problem. Took the car on a long trip (~ 600 miles, with a pause for 3 days in the middle) and it ran fine (but, again, a bit rich).

3 days ago, refilled my gas tank at a different gas station than the one above. Parked the car for 2 days, and in the morning tried to start it. Engine started but when i started pulling out of the parking slot, it felt weak and didnt want to go past 1500-1800 rpms. I drove it for a few minutes, and it didnt improve. After it had warmed up, it ran fine. I checked fuel trims and long term trims were high (15-18%). I got pending codes p0172/5, but no CEL.

Any ideas what could be causing this? Is there a way to confirm if one or more injectors are leaking?
I asked a technician (who does NOT specialize in lexus/toyota), after explaining the above and the below, who said that it could be fuel vapor escaping the fuel tank to the engine while the car is parked for a long period with a full tank. Could this be it?

Short fuel trims, when i looked at live data, were varrying between -5% and +5-8%. Fuel cap is genuine Toyota and new. Gas tank holds pressure properly (you hear the air/fuel vapors coming out when you remove the fuel cap). MAF sensor is new (genuine toyota) and seems to run fine (looked at live data during idle and @2500 rpms and they were within spec). Fuel pressure regulator seems also fine, based on the live data (pressure increases/decreases with rpms). The coolant temp sensor feels slugish (i started the car and ran it for 90 secs @2500 and it didnt reach 75C; it reached 71C after around 150 secs @2500. The starting coolant temp was around 30C, so it's not due to cold weather). I'm not sure about this, but seing how cheap it is, i placed an order for a new one anyway.

thanks for your help!

 

Hi

Please, could you open the oil tap and check if the oil smell gas?

Perhaps you are affected by TSB EG007-06, but this TSB affected the 2006 cars.

2006 - 2006 model year Lexus IS250 vehicles equipped with the 4GR–FSE engine produced BEFORE the Production Change Effective VINs shown.

Under certain driving conditions, some 2006 model year IS 250 vehicles may exhibit a M.I.L. “ON” condition with one or both of the following DTCs:
􀀀 P0172 (System Too Rich [Bank 1])
􀀀 P0175 (System Too Rich [Bank 2])
The Engine Control Module (ECM) (SAE term: Powertrain Control Module/PCM) logic has been modified to improve this condition.

Regards