91 4.0
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O2s have 4 wires, a 12v and ground for the heater
and 2 wires for the sensor part
The O2 sensor part generates its own voltage, so there is no voltage supplied by the vehicle to the sensor, just the heater
O2s need to be heated above 650degF to start generating voltage in the presence of Oxygen, they can't see fuel just Oxygen
High oxygen is less voltage, 0.1volt is high oxygen
0.9v is low oxygen
Its always under 1volt
O2s are the ONLY sensors that wear out, the chemical used runs out, 100k miles or 12 years is the life expectancy of an O2, which ever comes first
Variable reluctance(VR) sensors also generate their own voltage, crank sensors, cam sensors, ABS wheel sensors and speed sensors are usually VR type sensors, just FYI
O2s have 4 wires, a 12v and ground for the heater
and 2 wires for the sensor part
The O2 sensor part generates its own voltage, so there is no voltage supplied by the vehicle to the sensor, just the heater
O2s need to be heated above 650degF to start generating voltage in the presence of Oxygen, they can't see fuel just Oxygen
High oxygen is less voltage, 0.1volt is high oxygen
0.9v is low oxygen
Its always under 1volt
O2s are the ONLY sensors that wear out, the chemical used runs out, 100k miles or 12 years is the life expectancy of an O2, which ever comes first
Variable reluctance(VR) sensors also generate their own voltage, crank sensors, cam sensors, ABS wheel sensors and speed sensors are usually VR type sensors, just FYI
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Joined: Mar 2022
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From: LAKEWOOD
So I tested the o2 sensor. Bench test. Heat to the sensor end and only got .1 volts. It did not raise and lower when the heat was added and taken awy. The o2 sensor was replaced with an oem o2 sensor. Pulled the battery cables off and held them togeather for 30 seconds. Connected the cables and drove for about 10 miles. Pulled the code 41r again. No check engine light but still smell raw fuel out the tail pipe.
Traced the o2 wires through the harness and connections to the computer. wires and connections looked good.
Do you have any tips on what to do now?
Luther
Traced the o2 wires through the harness and connections to the computer. wires and connections looked good.
Do you have any tips on what to do now?
Luther
41 (R) System lean - Fuel control
(M) System was lean for 15 seconds or more (no HO2S switching) - Fuel control
So engine must have a major misfire in at least 2 cylinders
Lean and Rich with engine computers is about the Oxygen in exhaust not fuel, that's what O2s see, oxygen
If a cylinder misfires then no oxygen was burned up(and no fuel) so the O2 sensors see that extra oxygen sent into the exhaust as LEAN, high oxygen
And you smell the unburned fuel out the tail pipe
So IF the engine is misfiring then you need to solve that issue first, the 41 code is not the cause of a misfire, its the result of a misfire
4.0ls like to burn out spark plugs, Motorcraft or autolite seem to last the longest, NGK would be next
Big gap, 0.054"
Only use regular copper or Double coating, single coating is a waste of money when there is a Coil Pack
Spark plug wires last 15 years maybe, 10-12 years to be on the safe side
1991 computers, any engine computer older than 20 years, can get leaking capacitors, $5 fix, there are 3, open up computer and have a look, they are usually blue and easy to see
Can be seen here: Ford EEC-IV
Look for discolored area under the capacitor
(M) System was lean for 15 seconds or more (no HO2S switching) - Fuel control
So engine must have a major misfire in at least 2 cylinders
Lean and Rich with engine computers is about the Oxygen in exhaust not fuel, that's what O2s see, oxygen
If a cylinder misfires then no oxygen was burned up(and no fuel) so the O2 sensors see that extra oxygen sent into the exhaust as LEAN, high oxygen
And you smell the unburned fuel out the tail pipe
So IF the engine is misfiring then you need to solve that issue first, the 41 code is not the cause of a misfire, its the result of a misfire
4.0ls like to burn out spark plugs, Motorcraft or autolite seem to last the longest, NGK would be next
Big gap, 0.054"
Only use regular copper or Double coating, single coating is a waste of money when there is a Coil Pack
Spark plug wires last 15 years maybe, 10-12 years to be on the safe side
1991 computers, any engine computer older than 20 years, can get leaking capacitors, $5 fix, there are 3, open up computer and have a look, they are usually blue and easy to see
Can be seen here: Ford EEC-IV
Look for discolored area under the capacitor
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