Check Engine light shows Lean in Bank 1 and Bank 2

[BillRod]

Hi All

Just replaced my wife's 94 with a 2000 Ranger.

A week after I bought it the Check Engine light lit up with the codes for Lean in Bank 1 and Lean in Bank 2.

I have not found anything obvious.
What would be the best list of things to look for?

Any advice would be greatly appreciated.

It is a 2000, 4.0L OHV, Automatic, 4WD, Extended cab, 166,000 miles.

Thanks in advance!
Bill

 

[RonD]

Lean on BOTH banks(sides) means it not an O2 sensor issue, two O2 sensors would have to fail at exactly the same time, could happen, but winning lottery would be better odds, lol

Lean on BOTH banks means it IS something that can effect both banks
MAF sensor, Clean it

Upper intake vacuum leak, after engine is fully warmed up, and idling, unplug IAC valve's 2 wire connector, RPMs should drop to 500 or engine may stall, either is GOOD, it means no vacuum leak.
If idle doesn't drop then there is a leak.

Fuel Pressure, 2000 computer expects minimum 55psi fuel pressure, if its lower then Lean code would be set for both banks
Change fuel filter every 5 years or so, dirty filter can lower pressure at the engine

Lean code does NOT mean engine is actually running Lean, what it means is that the Computers air:fuel ratio calculations are off, computer is having to add at least 20% more fuel than it calculated based on air flow.
This means either the Air data(MAF sensor) is incorrect, or there is unreported air coming in(vacuum leak) or Fuel pressure is lower than expected so computer "thinks" it is adding more fuel than needed.


Other possibilities are partially blocked exhaust, you would notice engine horse power dropping off at high loads, like at highway speed, engine would be sluggish
Same symptom can happen with dirty fuel filter

 

[auendave1]

vaccum leaks are common

check the rubber 90 degree connectors on the pvc tube at front and rear of engine also brake booster gromet