The issues keep piling up - '91 2.9 runs rich, shuts off, codes 41 & 42...

[Fairlaniac]

Here is a link to my question on code 41. http://www.therangerstation.com/forums/showthread.php?t=164517
Nothing solved yet but now today while cruising along about 65-70 mph the engine seemed to momentarily shut off and immediately refire? It happened 3 times. All power to the rear just dies, I can't tell if it actually shut off completely or lost fuel? It happens so quick and then back up to speed. So I get home and check codes. I now have KOEO code 41 and KOER code 42. Never had the 42? Any ideas???

Thanks,

 

[RonD]

As someone said before codes 41 or 42 can't be set until O2 sensors warm up.
O2 sensors need to be above 600degF before they can work accurately, so while engine and exhaust pipe warms up computer runs in Open Loop, no feedback from O2 sensors, it use factory pre-set air/fuel mix stored in it's memory.
When O2 sensors start working, computer checks them during warm up, the computer switches to Closed Loop, and at that time it may set code 41 or 42 if O2 sensors are not responding correctly.
Computer adjusts open time for injectors at least 10 time per second, monitoring O2 sensors while it does this, if O2 sensors are not switching fast enough or is still showing Lean after adding more fuel it will set code 41.

Code 41 Lean and Code 42 Rich means computer has a split personality, lol

You only have one O2 sensor for both banks on the 2.9l right?

O2 sensors detect Oxygen not fuel so code 41 means too much oxygen in exhaust.
And it also means computer is adding extra fuel because O2 sensor is detecting too much oxygen in the exhaust.
Since your MPG went down and exhaust smells rich then there is a problem with computer, O2 sensor OR an exhaust leak.

An exhaust leak, upstream of O2 sensor, sucks air in, O2 sees the extra air as too much oxygen so computer adds more fuel.
Now engine is running rich because of false Lean, and MPG drops.

O2 sensor or wiring could be bad, you changed O2 sensor but how is wiring?
The switch to code 42 could point to bad wire(s)
O2 sensor will have 4 wires, 2 are power and ground for heater, O2 sensors are heated so they warm up faster and stay warm.
Then a Computer Ground wire, pin 46, and a voltage wire for computer to monitor O2 sensor

Computer could be misreading O2 sensor, O2 sensor generates its own voltage, .1 to .9volts, so not much but this voltage travels to computer is is read by a circuit in the computer.
Pins 29 or 39 on computer should have O2 sensor voltage

And pop the top on computer, have a look at the circuit board, black parts are from leaking capacitors and can be failed areas.

Good look here at what circuit board should look like: http://www.auto-diagnostics.info/ford_eec_iv


I don't think vacuum leak on this because while this would get code 41, engine wouldn't actually be running rich, it would be running normal for the most part because air leak is on the intake side, this shows up on O2 sensor as Lean at first but computer adds correct amount of fuel fairly fast so exhaust is back to correct oxygen levels.
Lean code 41 is set because computer calculation of 14:1 ratio based in MAP sensor data is incorrect, so code 41 in this case would be computer telling driver calculations are wrong.
So check MAP sensor or for vacuum leaks.

Actually running rich with a Lean code means Exhaust reading is not right, as said above, computer, O2 or exhaust leak

 

[Fairlaniac]

Thank you for the detailed post, this gives me something to work with.

There is only one O2 sensor on my 2.9.

 

[RonD]

I forgot to mention, that a consistent misfire, dumps unburned oxygen into the exhaust system, so O2 sees Lean, and runs other cylinders Richer to get oxygen levels in exhaust correct.

 

[Fairlaniac]

RonD, Thanks for your help. Do you have any comments on the sudden loss of power but back within a second?

Thanks,

 

[RonD]

Fuel pump cutting off

 

[Fairlaniac]

Not saying it can't be but pump is less than one year old?

 

[RonD]

If you put in a Ford(Motorcraft) fuel pump then no, it won't be the pump, if it was a 3rd party fuel pump then it probably is, there are a few brands that tend to start failing between 6 to 18months, usually under warranty but not always.

 

[Fairlaniac]

Put a new Actron fuel pressure test gauge on the Ranger. Take a look https://www.youtube.com/watch?v=f3TlpL3yp-4

Any comments on what to check for? Thanks!

 

[RonD]

Can view video, says Private

What does it show?

 

[Fairlaniac]

Sorry, I reset it to public. Try again. It shows a very erratic gauge. Very erratic???

 

[SenorNoob]

It looks like the pressure is dropping between every turn of the fuel pump. I'd suspect bad pump or major leak.

Sent from my MotoE2(4G-LTE) using Tapatalk

 

[Fairlaniac]

Put a new filter in today. Pressure steady at 35 psi. Now to find a chart somewhere that says that is within reason? Any idea of required pressure range?

Thanks!

 

[RonD]

1991 should be 30-42psi

Unplug the vacuum hose on fuel pressure regulator with engine idling, that will show max fuel pressure, with vacuum line plugged in at 650rpm idle you see minimum fuel pressure.

And with vacuum hose connected raise RPMs to approx. 2,000 and hold it there, pressure should be stable, not slowly dropping.

 

[Fairlaniac]

Same book, new chapter. After the install of the fuel filter and having the pressure stabilized I did not get a chance to do more over the weekend. So this morning I decided to drive the Ranger to work. 15 minutes into the drive the engine shut off and the check engine light flashed simultaneously. I don.t know if the light came on first and the engine shut off or not? Not sure if it matters. I fired it up and took off and it shut off again. It cut in an out 6-7 times bucking like a bronco and the check engine light was coming on with each cut out. Finally I'm dead on the side of the road. After a minute or two it did start and I limped it home. After about 10 minutes the check engine light came on and stayed on until I got home. Flipped the key back on and the CEL was out at that time. No time to check anything, jumped in the F250 and went to work. When it was temporarily dead along the road I did notice an odor. It wasn't and kind of engine smoke but it had a smoky sense but had a hint of electrical? Sounds like I'm describing wine Anyhow, I'll look at it tonight :-(