2.9L & 3.0L V6 Tech General discussion of 2.9L and 3.0L V6 Ford Ranger engines.

2004 3.0L Misfire

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Old May 18, 2022
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LethalLima51's Avatar
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From: Fresno, Ca
2004 3.0L Misfire

Recently joined this forum, but have been a frequent visitor for some time. I would first like to thank all of you for sharing your knowledge and taking the time to guide others in the right direction!

As far as the title of my post, I am going thru what a vast majority of everyone who has that engine will inevitably go through. I have tried just about everything talked about on many threads here. I have not replaced the 02 sensors with new ones, as I am unsure if that will solve anything. I have however swapped them with some from the wrecking yard and the fuel trims always show something similar to this photo I’ll be attaching. I pulled this freeze frame today. Could my 02 sensors be causing all this or could it be a damaged pcm?

I have successfully flashed a pcm on my 2007 mustang with FJDS after bricking it with a Holley tuner. So I do have that option as well. Thank you guys in advance for any and all suggestions/advice
 
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Old May 18, 2022
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Welcome to the forum

O2 sensors use a chemical to generate their own voltage, 0.1v to 0.9v so not much
They start to run out of chemicals at about 100k miles or 12 years which ever comes first
O2 sensors are the ONLY sensors that wear out

So...........Wrecking yard O2s are NOT a good idea, and O2s after 2012 or so are Wide Band, our Rangers all used narrow band

99% means O2 is disconnected, or broken, it is the default value
Bad O2 can't cause a misfire

When there is a misfire the first thing to do is a compression test to take compression off the table as the cause or find out it is the cause and not waste money on non-fixes
Remove all 6 spark plugs first
Test compression, write down results

A bad spark plug or bad injector can cause a misfire, they are also the least likely to cause a misfire
Burnt exhaust valve is the most common cause, because it lowers the compression in that cylinder so it misfires

But replacing the 6 spark plugs is fine, they also wear out, so most do that first, but THEN do the compression test
 
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Old May 23, 2022
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From: Fresno, Ca
Thank you for all the information and knowledge you pass down on these forums RonD. I certainly have benefited from them, I did go out earlier in the week and buy a compression tester earlier in the week, but did not have time to have a go at it. For some reason tho, earlier today I figured I’d change the spark plugs for like the third time in 5 months lol. To my surprise tho, the truck is idling beautiful and I only changed out the three on bank 2 (cyl’s. 4,5,6). They only had 4 in stock at the parts store I went to so I figured I’d get the other two tomorrow and swap them in. The plugs I was running before were “Motorcraft AGSF22FM”. I believe the guy at the counter gave me those instead of “AGSF32FM” either way what I am running now are the “Motorcraft AGSF32N or SP413”. Fuel trims instantly have dropped and the idle is worlds apart now & that’s with only one bank running the “SP413’s”. Attached is a screenshot of some of the parameters I was monitoring earlier after the change.
 
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Old May 23, 2022
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O2's have a placement designation "Sensor 1's" are the O2's closest to the engine, "Sensor 2's" are after the Cat Converters
V6 or V8 engines have "Banks", Left side(drivers side) and Right side(passenger side)
Sensor 1's are also called Upstream sensors
Sensor 2's Downstream

They are all the same type of sensor, interchangeable in placement

So O2 Bank 2 sensor 1 is the O2 sensor on Drivers side closest to the engine, aka, O2S21, O2 Sensor Bank 2 sensor 1

O2s generate their own voltage
0.1v high oxygen, lean
0.9v low oxygen, rich

The Sensor 1 voltage should jump around like crazy , but stay between 0.2v and 0.6v, 0.4v is the sweet spot
Sensor 2's are after the Cats so almost all the oxygen in the exhaust was burned up by the Cats, they should be steadier, and 0.7v to 0.9v is expected

Your sensor 1's are too low at 0.1v
Perhaps it was just the timing of the screen shot
Fuel trims look fine
 
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