Lean Codes on BOTH banks 4.0 2002
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Lean Codes on BOTH banks 4.0 2002
I have tried just about everything with this ranger. if it has to do with air fuel mixing, I've done it all. (Fuel pump, fuel filter, fuel pressure regulator, has NO VACCUM LEAK, MAF sensor, o2 Sensors, SPARK PLUGS/WIRES, ect. ect.) The only thing i haven't done is injectors. Still getting lean codes. Also misfires on 3 and 6 and has trouble up hills, as well as randomly through the drive. It will run fine for a bit but then the computer dumps max fuel in for seemingly no reason. Anyone have ANY ideas? For some background I've put 3 fuel pumps in this thing and every time it runs fine for a couple months and then it will be lean again all of a sudden. Bad computer? Do i need to do injectors too? Is the EGR letting gas in? I'm truly confused with this truck. Thanks guys.
Misfires on 3 and 6 would cause Lean codes on both banks
O2 sensor only see Oxygen, so a misfire does not burn any oxygen and O2 sees that oxygen when its dumped into the exhaust, so "lean" exhaust
Lean code doesn't mean the engine is actually running Lean, it means there is too much oxygen on that bank of the engine
If engine is pinging/knocking then its actually running Lean
And if its smoking its actually running Rich
Computer responds to too much oxygen in the exhaust by adding more fuel, thats what the "lean" means to computer
Computer increases open time for the injectors to add more fuel, the fuel trims go above +20% and thats when lean codes are set
If it gets better after putting in a new fuel pump then I would say you found the issue, well at least one of them
Try Motorcraft fuel pump, they are pricey but they last
I don't think 2002 4.0l has a fuel pressure test port, but you might be able to add one
The 3 and 6 misfires would be next on the list, until that's fixed the lean codes are meaningless
Injectors are pretty far down on the list to cause any issues, they can of course, anything can break, lol
Run some Seafoam or similar injector cleaner in the gas tank
Check spark plugs on 3 and 6 and at least 2 other cylinders to see what the tips tell you about whats happening inside the cylinders, light brown color means all is well, blackish is oil getting in, whitish is misfiring
O2 sensor only see Oxygen, so a misfire does not burn any oxygen and O2 sees that oxygen when its dumped into the exhaust, so "lean" exhaust
Lean code doesn't mean the engine is actually running Lean, it means there is too much oxygen on that bank of the engine
If engine is pinging/knocking then its actually running Lean
And if its smoking its actually running Rich
Computer responds to too much oxygen in the exhaust by adding more fuel, thats what the "lean" means to computer
Computer increases open time for the injectors to add more fuel, the fuel trims go above +20% and thats when lean codes are set
If it gets better after putting in a new fuel pump then I would say you found the issue, well at least one of them
Try Motorcraft fuel pump, they are pricey but they last
I don't think 2002 4.0l has a fuel pressure test port, but you might be able to add one
The 3 and 6 misfires would be next on the list, until that's fixed the lean codes are meaningless
Injectors are pretty far down on the list to cause any issues, they can of course, anything can break, lol
Run some Seafoam or similar injector cleaner in the gas tank
Check spark plugs on 3 and 6 and at least 2 other cylinders to see what the tips tell you about whats happening inside the cylinders, light brown color means all is well, blackish is oil getting in, whitish is misfiring
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Sep 6, 2021 10:52 AM
