Lexus IS250 - P0172 & P0175 (Bank system too rich) HELP!

[Sponelis]

Hi all. I have got Lexus IS250 2007. Couple of days ago check engine light and check VSC came on at the same time. My mechanic tried to diagnose the car and got codes P0172 and P0175, both banks are too rich. He did some more tests and the long term fuel trims were showing -25. All of the sudden something happened to the engine and fuel trims became normal. He is not sure what is causing it. Reading the forums, everyone is saying MAF sensor, but he said it can’t be as he was getting good reading from it. Anyone has any suggestions what could it be and what to do next to identify the problem?

[Mr Vlad]

Hi Simonas and welcome to the best Lexus forum there is. Regards your issue. No harm in cleaning the MAF sensor with a dedicated spray. 

What kind of fuel do you use? How does your car drive? Is it sluggish? Do you get any smoke from your exhaust? 

If your car drives normally then disconnect your Battery and leave it disconnected for 45 minutes. Re connect the Battery and see if the warning lights appear on the dash. If they don't then all good.

If they reappear after a short time then use a fuel additive like Millers Oils petrol ecomax. It cleans injectors and the fuel system and peps up the petrol. 

[Sponelis]

1 hour ago, Mr Vlad said:

Hi Simonas and welcome to the best Lexus forum there is. Regards your issue. No harm in cleaning the MAF sensor with a dedicated spray. 

What kind of fuel do you use? How does your car drive? Is it sluggish? Do you get any smoke from your exhaust? 

If your car drives normally then disconnect your battery and leave it disconnected for 45 minutes. Re connect the battery and see if the warning lights appear on the dash. If they don't then all good.

If they reappear after a short time then use a fuel additive like Millers Oils petrol ecomax. It cleans injectors and the fuel system and peps up the petrol. 

Hi Mr Vlad,

I use E5, car drives perfectly fine, however couple of times I had revs going up and down on its own when idling and then it stopped after like half a minute. Haven't seen any smoke from exhaust, apart from early morning on cold start, which I assume is normal.

Lights have been cleared by my mechanic today, I drove circa 40 miles afterwards and it hasn't reappeared yet.

Ill try to clean MAF. I could try the additive as well, but my mechanic said it shouldn't be anything wrong with the injectors as error code is appearing on both banks, meaning something else triggered it.

[Mr Vlad]

That's good then. One thing to check. The PCV valve. How many miles on your car? A faulty PCV valve can cause similar issues. It's very awkward to check. You could check the condition of the throttle body butterfly valve. Just take off the air pipe going to it and see how dirty or not the chamber is. DO NOT move the butterfly valve until you've either disconnected the Battery or the multiplug on the throttle body itself.