3.0 flex ecu & injector difference. p172 & 175.

[pat.m]

Big thanks in advance to the person that can answer this question. I have a p172 &175 running rich issue. Its a 2002 Ranger 3.0 Edge. I have diagnosed the issue being that someone has installed flex fuel injectors in a non Flex 3.0. (8th digit vin is a u, also injector o-rings are green indicating flex injectors) knowing that the flow lb's per hour of the flex injectors is overrated for this engine do I need to physically swap out the 6 injectors to the correct part number ,or is re programming the ECU with newer flex software possible?

 

[stmitch]

At some point (I believe around 2001-2002) Ford quit using a flex fuel sensor, and the fuel octane was determined in the PCM using the O2 sensor data. This would be good news for you if your truck doesn't have a flex fuel sensor on the inside of the frame under the driver's seat. That would mean injectors and PCM are the only significant differences, and if the PCM can be reprogrammed with a flex fuel tune you'd be fine.

That being said, I've been around various Ranger forums and have special interest in flex fuel 3.0s for 15 years. In that time I don't think I've heard of anyone attempting to reprogram a non flex fuel PCM into a flex fuel PCM. I can't honestly say if it would work or not.

You can reprogram the PCM (whether flex or not) to add more fuel when larger injectors are installed, so I'd assume that you could go the other way, and set the injectors to open for a shorter time as well, essentially downsizing your injectors. This might fix your rich condition, but it would not give you actual flex fuel ability to change fuels on the fly or run e85. An aftermarket tune is usually a few hundred bucks though, which is probably really close to what replacement injectors would cost.

Does increasing the ethanol content to something like e15 impact your rich condition at all? It might be worth a shot to try.

 

[RonD]

Welcome to TRS

You will need to change all 6 injectors

The PCM is programed for fuel pressure(55psi) and injector size
So it knows exactly how much fuel will come out of each injector if it is opened for say 100milliseconds
The larger flex fuel injectors are sending out more fuel so the computer has to close the injectors at least 20% sooner than calculated, so "Rich" codes

Yes, you could swap in a Flex fuel computer, or even reduce fuel pressure(wouldn't recommend the latter, lol)

Probably could try to reprogram, but all in all selling your flex fuel injectors and buying used or new ones would be better long term

And just as a heads up, previous owner may have swapped in a whole flex fuel engine...............just a thought, there would be no reason to swap in flex fuel injectors on their own

 

[pat.m]

At some point (I believe around 2001-2002) Ford quit using a flex fuel sensor, and the fuel octane was determined in the PCM using the O2 sensor data. This would be good news for you if your truck doesn't have a flex fuel sensor on the inside of the frame under the driver's seat. That would mean injectors and PCM are the only significant differences, and if the PCM can be reprogrammed with a flex fuel tune you'd be fine.

That being said, I've been around various Ranger forums and have special interest in flex fuel 3.0s for 15 years. In that time I don't think I've heard of anyone attempting to reprogram a non flex fuel PCM into a flex fuel PCM. I can't honestly say if it would work or not.

You can reprogram the PCM (whether flex or not) to add more fuel when larger injectors are installed, so I'd assume that you could go the other way, and set the injectors to open for a shorter time as well, essentially downsizing your injectors. This might fix your rich condition, but it would not give you actual flex fuel ability to change fuels on the fly or run e85. An aftermarket tune is usually a few hundred bucks though, which is probably really close to what replacement injectors would cost.

Does increasing the ethanol content to something like e15 impact your rich condition at all? It might be worth a shot to try.

Thanks for the good info. I'll check for the flex sensor.

Welcome to TRS

You will need to change all 6 injectors

The PCM is programed for fuel pressure(55psi) and injector size
So it knows exactly how much fuel will come out of each injector if it is opened for say 100milliseconds
The larger flex fuel injectors are sending out more fuel so the computer has to close the injectors at least 20% sooner than calculated, so "Rich" codes

Yes, you could swap in a Flex fuel computer, or even reduce fuel pressure(wouldn't recommend the latter, lol)

Probably could try to reprogram, but all in all selling your flex fuel injectors and buying used or new ones would be better long term

And just as a heads up, previous owner may have swapped in a whole flex fuel engine...............just a thought, there would be no reason to swap in flex fuel injectors on their own

that's good info, I appreciate it. I did observe fuel pressure of 55 PSI at the fuel rail both cycling the ignition/engine off and running. Also the oxygen sensors are new. The truck is new to me, I got it off a small dealer that could not diagnose it Haha. anyway I did watch the live stream data on the fuel trim. it does not even start out with short term trim, then leading to long term readings afterwards. I cleared the dtc's, fired it up and it literally went directly back to 30% fuel trim.
My understanding is that the flex injectors are 22.5lb/hr vs the non flex at 13.5lb/hr. Obviously if for some reason the injectors did get mixed up, that's why it's so rich!
What's the best way to confirm my engine being factory flex or not?? as said earlier the vin indicates a non flex engine. I don't see signs of an engine swap, but it could have been done a long time ago.

 

[RonD]

Gasoline uses 14.7:1 air:fuel mix ratio, E85 Ethanol uses 9.8:1 ratio so alot more E85 needs to be added every RPM which is why it needs the higher flow injectors, high pounds per hour
These are WEIGHT Ratios, just FYI, and why lb/hour is used
14.7 Pounds of air to 1 Pound of gasoline
And why "pre-vaporizors" and 200MPG carbs were fantasy at best and scams at worst

Rangers VIN with 3.0l used U for gas only and V for Flex
VIN say "gas only" so that would be the computer used

Looks like you correctly diagnosed the symptom, I don't think any one would put in the wrong injectors by accident
Maybe previous owners was confusing Jets with injectors, more fuel is better, but its not, more air is better, lol, then you can add more fuel

Now you could install a turbo charger(more air), you have the injectors for it