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Re:Diverging fuel trims, help me understand
- Speedwagon
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3 years 2 weeks ago - 3 years 2 weeks ago #47941
by Speedwagon
Diverging fuel trims, help me understand was created by Speedwagon
2002 Ford Explorer 4.0. Idles ok, but throws misifire codes on bank 2 when under load, and doesn't want to climb anything somewhat steep faster than about 45mph.
I was looking at several data points, and noticed the fuel trims diverge from each other when the vehicle is climbing.
The other odd thing I'm seeing, is the fuel trims and O2 sensors flatline when the cruise control is set
Is this telling me the O2 sensors are going bad? They appear to be original to the vehicle (connector colors match the vehicle connector colors), and it has 200k miles.
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I was looking at several data points, and noticed the fuel trims diverge from each other when the vehicle is climbing.
The other odd thing I'm seeing, is the fuel trims and O2 sensors flatline when the cruise control is set
Is this telling me the O2 sensors are going bad? They appear to be original to the vehicle (connector colors match the vehicle connector colors), and it has 200k miles.
Last edit: 3 years 2 weeks ago by Speedwagon.
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3 years 2 weeks ago #47951
by Speedwagon
Replied by Speedwagon on topic Diverging fuel trims, help me understand
Turns out, I have an 'error' for bank 2 fuel loop. Before is idle, and 2500 rpm in neutral
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3 years 2 weeks ago - 3 years 2 weeks ago #47975
by Speedwagon
Replied by Speedwagon on topic Diverging fuel trims, help me understand
Appreciate that info.
Trying to eliminate things, just did a compression test. 145-152 on all cylinders (warmed up for a few minutes, but not at operating temp, and at 5000ft Denver)
Resistant check all injectors, 15.5-15.8 warm (cold, they all measured around 14.5 if I recall correctly)
edit to add: Injector pressure drop test, starting at 59 psi on each, I got 30, 31, 30, 32, 32, 30
These are the plugs. 1 in bottom left. Doesn't look like 3 is firing correctly.
Trying to eliminate things, just did a compression test. 145-152 on all cylinders (warmed up for a few minutes, but not at operating temp, and at 5000ft Denver)
Resistant check all injectors, 15.5-15.8 warm (cold, they all measured around 14.5 if I recall correctly)
edit to add: Injector pressure drop test, starting at 59 psi on each, I got 30, 31, 30, 32, 32, 30
These are the plugs. 1 in bottom left. Doesn't look like 3 is firing correctly.
Last edit: 3 years 2 weeks ago by Speedwagon.
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3 years 2 weeks ago #47982
by Matt T
#3 looks a lot newer than the other plugs. Maybe it ain't been in there long enough to get dirty? Do you know the history on this vehicle?
Replied by Matt T on topic Diverging fuel trims, help me understand
Speedwagon wrote: These are the plugs. 1 in bottom left. Doesn't look like 3 is firing correctly.
#3 looks a lot newer than the other plugs. Maybe it ain't been in there long enough to get dirty? Do you know the history on this vehicle?
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3 years 2 weeks ago - 3 years 2 weeks ago #47985
by Speedwagon
Replied by Speedwagon on topic Diverging fuel trims, help me understand
I had to let off the throttle for it to shift info second.
I just figured out I can rig my compression tester hose to my vacuum/carb fuel pressure tester, and make it an exhaust back pressure gauge. So once it cools off a bit, I'm going to try that out.
I just figured out I can rig my compression tester hose to my vacuum/carb fuel pressure tester, and make it an exhaust back pressure gauge. So once it cools off a bit, I'm going to try that out.
Last edit: 3 years 2 weeks ago by Speedwagon.
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3 years 2 weeks ago #47986
by Tyler
Replied by Tyler on topic Diverging fuel trims, help me understand
Thanks for that capture! Confirmed terrible VE:
Note that I added the actual BARO reading for Denver, which is currently 30ish inHg according to Google. But that's not what the scan data said.
The scan data says the local BARO is 72.something kPa, which is closer to 9000 feet. That's because the BARO is calculated by the PCM based on MAF readings. Because the engine isn't breathing correctly, the BARO calculation is impacted. With the skewed BARO reading, the VE numbers look like this:
That's closer to what they SHOULD be. But the first calculation tells the real story. I still maintain you're looking at a plugged cat on bank two. A timing problem is possible, but you'd think it'd show in the static compression readings.
Note that I added the actual BARO reading for Denver, which is currently 30ish inHg according to Google. But that's not what the scan data said.
The scan data says the local BARO is 72.something kPa, which is closer to 9000 feet. That's because the BARO is calculated by the PCM based on MAF readings. Because the engine isn't breathing correctly, the BARO calculation is impacted. With the skewed BARO reading, the VE numbers look like this:
That's closer to what they SHOULD be. But the first calculation tells the real story. I still maintain you're looking at a plugged cat on bank two. A timing problem is possible, but you'd think it'd show in the static compression readings.
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