I was just looking at my scan tool live data and noticed that both O2 bank 1 sensor 2 and O2 bank 2 sensor 2 short term fuel trim (STFT)shows N/A for both of them plus my spreadsheet of the data shows 99% STFT for both of them. The O2 sensor1 on both banks look "OK" with STFT varying between -5% and +5%. What say you guys? Did I lose 2 O2 sensors in the sensor 2 positions? Should I change all 4 at the same time? Looks like the sensors are inexpensive though.
I forgot to mention that there are no codes tripped.
Clogged fuel filter, bad or failing fuel pump, bad or faulty map sensor, MAf, o2 sensors, vacuum leak, bad throttle body, gasket dirty throttle, pedal position sensor, manifold gasket.
This is the most common lean condition causes. I also included a chart that might help you. I think Scotty has a video how to read live data. You should watch a few and learn how to properly read live data. it will greatly help you in the future
Scottys scan tools pull a lot more data than my cheap BlueDriver.
I have 40 PSI of fuel line pressure so I have to say that the fuel pump and filter are OK. The throttle plate has been thoroughly cleaned and the gasket replaced. The IAC has been cleaned - when I find the new IAC gasket again I'll install it. MAF has been cleaned. I looked for vacuum leaks with propane but couldn't find any. Spark plugs were recently replaced. Replaced 4 coil plugs that didn't snap on to the coils. I guess I'll just live with it until codes pop up.
99% is Normal that's. That is the stft. It's a default number to keep it simple. What does the voltage read for your downstream when car is at running temp.
They start out at 0V and go as high as 500 miilivolts.
Look at your ltft and short term trims. Not the 02 but the trims itself for each bank. Combined you want it under 10% + or --
Bank 1 LTFT at idle is 9.4%, bank 2 8.6%.
I also forgot exhaust leak can cause a lean condition as well. It can even cause your o2 sensors to act up and even throw codes. Just yesterday in my Mercedes my exhaust gasket went bad had a small exhaust leak. It throw a codes for both o2 sensors and the car was running really lean . Bank. 2 stft was 15.7% bank 2 ltft was 18.8%. I replaced gasket and now its stft 0.09% and ltft is 0.02% . So a simple exhaust can cause issues. Including rough idle.
Your running lean. Are you having any performance issues or no
Just a small vibration at idle. Otherwise the car runs fine. But I only get an average of 14 MPG.
You don't need anything fancy or expensive. A cheap scanner that has live data is usually all you need. You just have to learn the basics on how to read it and understand it. The only time you need a scan tool like mine or Scotty is if you work on cars for a living. You can find some really good scan tools that are entry level for under 125. If you want something towards the middle you can find them between 300 to 500. I think there are a few that cost under 75 that can do alot
You have propane that's good. Does your scan tool let you graph at least 1 thing. Can you graph your o2 sensor voltages. If not you can still do something. Plug your tool in and bring it to front of car. Remove air box start car and introduce propane to air current. When you do this you will watch it max out at rich in few seconds or less. Now remove propane and watch data. There should be a slight delay followed by a steady but rapid readjustment of o2 data back to normal. Do that with both sensors. Now remove a main vacuum line and do the same. This time it will go lean. When you hook back up, it will readjust back to normal. It should act like it did when rich. If you do that and you have a really quick reacting to the Rich, lean condition with a slight delay that is rapid but steady to normal you confirmed that your o2 sensors and cats are good. Now if your cat is bad or failing this test won't work. Just let me know in detail how it goes and we'll go from there
Make sure the car is at least warmed up. If its to cold the results won't be accurate