Lean Bank 1 and normal Bank 2 low MPG 9 in city

[azharj]

Hi. every one!
280 K windstar 2000, LTFT or Bank 1 remains 3 to 6. bank 2 remains -0.8 or 0.8. Remains same at high RPM 1500 But at 2500 rpm LTFT becomes normal near zero or 0.8 + -. Changed bank one upstreamO2 sensor no effect. No missing. Mode 6 shows no missing. Plugs and wires are 2000 KM. No CEL. No rough idling. No drive-ability problem. No oil leakage. no effect on spraying gas on engine. 9MPG in city and 14 on freeway. engine coolant and engine oil is not loosing. Regularly change engine oil and transmission oil.Any idea???

[tomj76]

For the LTFT parameter, anything <25% or >-25% is OK (won't set a code). With numbers that with 5% of zero, I think you're engine is fine.

The imbalance can be caused by:
Leaking fuel injectors
Restricted fuel injectors
Leaking intake passages (vacuum leak)
Restricted intake passages
Incorrect oxygen sensor readings
Dirty valves
Worn valve train (particularly camshaft lobes)
Carbon building in combustion chambers
and more...

[azharj]

Thanks Tomj76. A few days ago, Keeping the reply by you, I took 4 bottles of Mitsubishi Injector Cleaner, poured in full tank and drove about 1000 miles on high highway in two days. I checked live data. Both banks same values for LTFT differing only by one or two. So I think off and on pouring Injector cleaner is a good idea.

[tomj76]

That's good information to see that FI cleaner helped. Gasoline is supposed to include FI cleaning solutions, but it sounds like an occasional boost can improve them a bit.

The interesting thing here is that a single "shot" of gasoline from a FI is very small (~1/1000 fl oz), so the difference (5%) is just 1/20000 fl oz. I suppose this shows that it doesn't take much restriction in the FI to cause that error.

[azharj]

Tomj

Agreed may be only driving at highway speed had caused the change. There are many YouTube video to clean carbon and catalyst converter by pouring one gallon lacquer thinner in full tank of gas. Don't know the truth.

[azharj]

In my opinion, finally the culprit found. In march 2023 while coming back from a leisure trip of 2300 Km in 3 days, it lost all power and acceleration and huge steam coming from behind the engine between the head and engine block ---head gasket leak. The gradually increasing the slow coolant leak was there, for the last a few years. The leak was into the cylinder No. one which started causing intermittent P0301 see also https://www.automotiveforums.com/vbu...hp?t=1158769it. During the repair work it was found that he heads were repaired during the repair of pervious head gasket leakage. These differed in the thickness slightly, and now these were irreparable. I bought the two heads from the junkyard. These were almost new. Now the STFT and LTFT is very nearly equal it differs only by 1 to 3 at the most. It runs well no code and improved mileage by two Km/ litre