98 3.0 FUEL TRIM


Ranger ray 61

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My 98 ford ranger 4x4 3.0 5 speed went south blew up so to speak. replaced with engine out of 1999 ranger with automatic trany. 3,0 used all of my intake and exhaust and sensors. my engine light came on. said truck running to rich .anyway long story short. it has been in two shops. the first shop updated ECM replaced map sensoror maf sensor checked for bad sensors.Took it from there second shop fount the injectors to be flex fuel. put the old injectors in and now lean condition did smoke test no air leak what i did to pass smog is put 1 flex fuel injector in each bank to keep my fuel trim 5 pluss to5 minuss to keep light off. but still nott right. the donner engine was hooked to automatic it now is hooked to 5 speed .Did i miss somthing also put new 02 sensors in it. also put new ecm in it and new injectos to specs in bank 1 no change
 


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RonD

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Welcome to the forum

If your 1998 computer was not programmed for Flex Fuel then yes it should set a Rich code if you use larger injectors(flex fuel used larger injectors)

Swapping back to original injectors would initially cause a Lean code because Long Term fuel trims had been adjusted for the larger injectors

There are two fuel trims, short term(STFT) and long term(LTFT)

You can not reset or clear Long term fuel trims, the point of this fuel trim is so vehicle can age gracefully, lol
There will be small air leaks and fuel pressure won't be at max after 10+ years, rings wear down and valve seals as well so compression is not like new, many things change in a vehicle and the engine over time
LTFT is there so computer doesn't have to adjust to these changes every time you start and drive the vehicle

So while you were running the larger injectors the LTFT would have been adjusting itself down into the -15% to -25% fuel trim area, Rich condition is "-" fuel trims, Lean is "+" fuel trims

Short term fuel trim's set 0 as Computers calculation + LTFT

When you put back in the regular injectors , computer doesn't "know this", so on start up computer calculates injector open time and then -20% from LTFT, well................, with the smaller injectors computer has to increase open time, +20% to get O2 sensors to show good oxygen levels, and over 15% either way sets a code, so you now get a Lean code

Run the engine for a few days and see if LTFT starts to come down, get closer to 0, it should, then you can reset/clear the Lean code and they shouldn't come back

And no, 3.0l Vulcan engine was the same manual or automatic
 
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Josh B

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Yeah, what RonD said ^^ haha

I can't really help you much with that, but can offer you an experience of my own that you might can relate. Sometimes you might be as well off to just replace the parts yourself. My situation concerned passing an emmissions inspection in a fairly tough city. After failing it once or maybe twice I took it to a shop, they wanted $250.00 to put it on a test machine, which was not even gauranteed accurate. After studying into the system best I could there were only 5 sensors involved, each cost appx $50.00 new. I took my best guess at the primary suspect and replaced it, $50.00, and took it back to emmissions. It passed the first time :)
 

Ranger ray 61

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Welcome to the forum

If your 1998 computer was not programmed for Flex Fuel then yes it should set a Rich code if you use larger injectors(flex fuel used larger injectors)

Swapping back to original injectors would initially cause a Lean code because Long Term fuel trims had been adjusted for the larger injectors

There are two fuel trims, short term(STFT) and long term(LTFT)

You can not reset or clear Long term fuel trims, the point of this fuel trim is so vehicle can age gracefully, lol
There will be small air leaks and fuel pressure won't be at max after 10+ years, rings wear down and valve seals as well so compression is not like new, many things change in a vehicle and the engine over time
LTFT is there so computer doesn't have to adjust to these changes every time you start and drive the vehicle

So while you were running the larger injectors the LTFT would have been adjusting itself down into the -15% to -25% fuel trim area, Rich condition is "-" fuel trims, Lean is "+" fuel trims

Short term fuel trim's set 0 as Computers calculation + LTFT

When you put back in the regular injectors , computer doesn't "know this", so on start up computer calculates injector open time and then -20% from LTFT, well................, with the smaller injectors computer has to increase open time, +20% to get O2 sensors to show good oxygen levels, and over 15% either way sets a code, so you now get a Lean code

Run the engine for a few days and see if LTFT starts to come down, get closer to 0, it should, then you can reset/clear the Lean code and they shouldn't come back

And no, 3.0l Vulcan engine was the same manual or automatic
 

Ranger ray 61

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I give up. Fuel trims have not changed in a month and a half I'm just going to put a piece of black tape over the light color fixed
 

adsm08

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LTFT can be cleared out. Anything that wipes out the PCM's keep alive memory, so a computer replacement, a software update, or a KAM reset will clear the LTFT.

Also, under certain conditions they will adjust rather quickly. If you have lean codes and an LTFT around 25% when you fix the air leak and start it up you can watch them drop like a rock.

Take your short terms at idle, and subtract them from, the long term at idle. Then do the same at 2500 RPM. If the results are more than 15 points different you have an air leak. If less than 15 you have a MAF issue.
 

Dirtman

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So friggin big!
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Maybe post what the actual DTC's are?
 

decipha

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if one of the shops rewrote the ecu theres no telling whats on it now

do you have any tuning devices or datalogging abilities?
 


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