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Jason's 96 F150 5.0


RonD

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Lean doesn't mean "lack of fuel" in the case of fuel injected engine computers
O2 sensors report only oxygen in exhaust not fuel

If a cylinder misfire then no oxygen was used up so all that oxygen goes into the exhaust to the O2
Computer response to O2s high oxygen by adding more fuel to that bank of the engine
Which in itself could cause misfire if a spark plug was weak

Old O2 does False Lean, and if there are two O2 sensors, on a V6 or V8, and only one is showing lean, then replacing BOTH upstream O2s would be first step, unless you have a steady misfire on that bank with the lean code
Computer has no comparison for O2s, they are "the word of God" as far as computer is concerned, so any O2 related codes ASSUME O2 is in PERFECT working order as far as computer is concerned
Which is why changing the O2, even swapping it around with another O2, is a good first thing to do with just the one code

Computer programmers have a long standing saying, since the first computers, lol, "Garbage in = Garbage out" meaning the result is totally reliant on the input
Most, if not all, computer "mistakes" come from bad "input"
 


ford4wd08

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Lean doesn't mean "lack of fuel" in the case of fuel injected engine computers
O2 sensors report only oxygen in exhaust not fuel

If a cylinder misfire then no oxygen was used up so all that oxygen goes into the exhaust to the O2
Computer response to O2s high oxygen by adding more fuel to that bank of the engine
Which in itself could cause misfire if a spark plug was weak

Old O2 does False Lean, and if there are two O2 sensors, on a V6 or V8, and only one is showing lean, then replacing BOTH upstream O2s would be first step, unless you have a steady misfire on that bank with the lean code
Computer has no comparison for O2s, they are "the word of God" as far as computer is concerned, so any O2 related codes ASSUME O2 is in PERFECT working order as far as computer is concerned
Which is why changing the O2, even swapping it around with another O2, is a good first thing to do with just the one code

Computer programmers have a long standing saying, since the first computers, lol, "Garbage in = Garbage out" meaning the result is totally reliant on the input
Most, if not all, computer "mistakes" come from bad "input"
I've replaced both upstream O2 sensors with new bosch units in the last 24 hours, no change in performance and miss is still there.....

P0174 code for lean bank 2 is still present after two new upstream O2 sensors.

I have replaced the ignition cap, rotor, plugs, and wires with Motorcraft replacements vs the junk the PO had put on.

So, where to go next?
 

19Walt93

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Supply pressure was 100 psi.

Did some more wrenching on it today. I think there is definitely something wrong with cylinder 1.

Not sure if it is worth tearing down to figure it out, or looking for a junkyard motor at this point....
Keep in mind then newest F series or Bronco 302 would be a 1996 and the newest Explorer would be a 2001. I'd be wary of an engine that old.
 

ford4wd08

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Keep in mind then newest F series or Bronco 302 would be a 1996 and the newest Explorer would be a 2001. I'd be wary of an engine that old.
True, might need to just rebuild this one if we get to that point. This vintage EFI is not my favorite as it leaves me with just not enough information to fix it... LOL
 
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RonD

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Use OBD2 reader to see the voltage of both upstream sensors after warm up
Voltage changes very fast so you are looking for a range, like .2v to .7v

If drivers side is not changing then its disconnected(broken sensor wire), which is 0.0v and Lean code

If it is changing then it shouldn't go above say 0.5v so can be a misfire, or an air leak in exhaust manifold on that side or air leak on intake manifold on that side
 

ford4wd08

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Use OBD2 reader to see the voltage of both upstream sensors after warm up
Voltage changes very fast so you are looking for a range, like .2v to .7v

If drivers side is not changing then its disconnected(broken sensor wire), which is 0.0v and Lean code

If it is changing then it shouldn't go above say 0.5v so can be a misfire, or an air leak in exhaust manifold on that side or air leak on intake manifold on that side
I believe that can be done by using Forscan since it is OBDII.

I'll pull number 1 cylinder again and check plug and probably due leak down and compression check as well.
 

RonD

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Just do leakdown

Compression test needs comparison to mean much, i.e. test at least 3 other cylinders to get an average, this allows for crank speed and gauge differences
Compression is transient/temporary, no way to get an air tight seal with metal on metal, lol
So the faster the crank spins the higher the number because there is less time to leak air
Gauges are often not calibrated for each use, lol, so testing at least 4 cylinders will give you this one day's average for gauge and crank speed

If all 4 cylinders tested were 120psi, that's a low number, but would mean no compression issue(unless time chain gear slipped, lol)
If 3 were 120 and 4th was 90 that would mean compression issue in the lower cylinder

If you just test just 1 and its 140psi you may think thats good, but if you test more cylinders and they are 170psi then 140 was not good
So comparison is needed


Leak down doesn't need a comparison, its a %


Yes Forscan can watch Live Data, even graph it while you REV engine to 1,500rpm and hold it there to watch what O2 voltage is doing
 
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19Walt93

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Before you get too involved check all the grounds- don't just look at them, remove them and make sure they're clean and tight. A local used car dealer brought us an F150 they'd put 5 O2 sensors on trying to a check engine light problem. The tech fixed a corroded ground in about 20 minutes. Their scanner was set up to give suggestions instead of trouble codes because training wasn't a priority for them.
 

ford4wd08

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Before you get too involved check all the grounds- don't just look at them, remove them and make sure they're clean and tight. A local used car dealer brought us an F150 they'd put 5 O2 sensors on trying to a check engine light problem. The tech fixed a corroded ground in about 20 minutes. Their scanner was set up to give suggestions instead of trouble codes because training wasn't a priority for them.
That is some good advice that I have overlooked good idea. I just need to work through a list and cross things off.
 

ford4wd08

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Just do leakdown

Compression test needs comparison to mean much, i.e. test at least 3 other cylinders to get an average, this allows for crank speed and gauge differences
Compression is transient/temporary, no way to get an air tight seal with metal on metal, lol
So the faster the crank spins the higher the number because there is less time to leak air
Gauges are often not calibrated for each use, lol, so testing at least 4 cylinders will give you this one day's average for gauge and crank speed

If all 4 cylinders tested were 120psi, that's a low number, but would mean no compression issue(unless time chain gear slipped, lol)
If 3 were 120 and 4th was 90 that would mean compression issue in the lower cylinder

If you just test just 1 and its 140psi you may think thats good, but if you test more cylinders and they are 170psi then 140 was not good
So comparison is needed


Leak down doesn't need a comparison, its a %


Yes Forscan can watch Live Data, even graph it while you REV engine to 1,500rpm and hold it there to watch what O2 voltage is doing
Leak down it is. I'll try to do it today.
 

ford4wd08

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Ok, @RonD I appreciate all you're good advice as usual.

Got to play with Froscan. O2 Sensor for Bank 2 upstream was jumping up over 0.7 volts and I snapped a screen shot of it at 0.88 volts.

Just to confirm, Bank 2 is the side with cylinder 2, in this case the passenger side of cylinders?

I'm going to look for misfire with the computer on cylinders 1 - 4.
 

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ford4wd08

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Also getting more detail on the P0174. Makes me wonder about the fuel pump as well, one has already failed, could be the other one? Guess I can check fuel pressure.
 

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RonD

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Bank 1 is passenger side
Bank 2 is drivers side on Fords
 

ford4wd08

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Bank 1 is passenger side
Bank 2 is drivers side on Fords
Thank you for that. I couldn't find that solid anywhere on the the Internet.
 

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All plugs are firing. I think I'm going to rent fuel pressure tester to see what I have at the Schrader valve on the driver's side fuel injectors.
 

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