This is from the factory manual

KOEO 45-60
KOER 50-60

and I have read that this should jump 5~10 if you remove the vacuum line whilst running.

SO I have 55 KOEO and only 45 KOER. It does jump to 55 when I removed the vacc line. I'm pretty sure I'lll be replacing that guy, but why would I be getting a 173 code? Running Rich?


1995 F150 4.9L 4x4 Manual

 

Your fuel pressures sound OK. Why would you want to replace the FPR. A new one may not work as well as your known good one?

 

Because its out of specs? 45 does not = 50-60

 

Subford is the guru on this and I agree with those fuel psi numbers as good.

Running rich per the PCM can be induced from a vacuum leak, though general thinking would say running lean if.there was a vac leak. But once the vac leak is big enough, the PCM can only widen the pulse rate so far for the injectors, thus the O2 sensors pick up the remaining amount, sends back info to try to narrow down the pulse width, but the unmetered vac leak needs extra fuel to burn, and thus you continue this cycle. PCM throws the CEL and hopes you can find the problem.

Could also be a lazy O2 sensor if It's an old one.

Do you still have all original nylon vacuum lines? Good chance 1 or more are broken, but you can't tell it.

 

If you have 45 psi running, then the PCM would sense a Lean condition. That's because the 4.9 uses 14lb injectors and another reason why the fuel psi is higher for these engines.

 

I just finished replacing a broken secondary AIR tube, new injectors, all new vac lines. New V.C. gasket and oil galley gasket. Previously rebuilt the Vac cannister. I think I have found and fixed all air leaks and oil leaks at this point. Newish 02 sensor last year. Looking at the plugs I would agree that she is running rich.

 

That is not what the factory manual says.
The factory manual for the 1995 4.9L says:
KOEO 50-60psi
KOER 45-60psi

The 45 is at idle with vacuum applied ot overcome the spring in the FPR.
The 55 is at or near WOT.
If you flip the throttle fast you may see a peak to 60 but this very doubtful.

The same goes for the V8 engines. The manual says that it will go from 28-45psi but you never see this as it will also be 5psi less around 40psi.

 

What's your vacuum at?

Have you checked the PCV valve?
Did you replace the PCV emissions hose? If so, did you use fuel line to do so?
Did you use any fuel line hose to replace vacuum/emission hoses?

What driveability problems led you to pulling codes?

You said you checked plugs and they show signs of running rich, when were they replaced?

Have you used a propane bottle and hose to spray around the intake for vacuum leaks or done a smoke test since your repairs?

Is the EGR functional and if so have you checked it for a vacuum leak?

 

The original injectors were leaking, causing hard starting. The spark plug base ring shows that she is running rich. I want to find the cause of this before replacement, but it could also be a contribuiting factor? Same with o2 sensor, after running rich previously. I need to test TPS and MAP

 

Timbersteel and Subford, thanks for your interest and guidance. I will address these questions ASAP but I have to get to work right now.

Mark

 

New silicone vac lines from siliconeintakes.com for brake boost and all vac lines. EVAP canister hoses replaced with fuel line hose. PCV is working good and hose is still original. Passes the shake test and sucks good. EGR is new, no vac at idle. The EGR solenoid is getting vac on lower port at idle. The plugs are about a year old same as 02 sensor. I had no codes before these repairs but CEL on immediatly afterwards. Truck runs better than ever before. Also getting code 167, 129 and 225 along with the 173. These codes have reappeared even after clearing memory. So I know that I need to check TPS and MAP as they work with 02 to determine air mix. I orignally thought these codes were operator error on the KOER test but they seem to be staying around. I have ordered a vac gauage so that I can test the MAP, just waiting for it to arrive. O.K. really got to run now.

Thanks

 

Not sure how you would check a MAP sensor with a vacuum gauge. Most use a tachometer meter to check the MAP sensor.

 

Part 2 -Manifold Absolute Pressure MAP Sensor Test (Ford 4.9L, 5.0L, 5.8L)

 

That way requires a meter that reads in Hz's.
You only said vacuum gauge.

The tachometer meter way:


On Ford applications, a multimeter that can read
frequency is normally required to check the sensor’s
output. But you can also use an ordinary tachometer
because a tach can display a frequency signal.
Here’s the procedure:


1. Set the tachometer to the four-cylinder scale
(regardless of how many cylinders the engine has).


2. Connect one tachometer lead to the middle terminal
on the MAP sensor and the other tachometer test
lead to ground.


3. Connect the two jumper cables the same as before,
attaching each end terminal on the sensor to its
respective wire in the wiring connector.


4. If you want to measure engine vacuum so you can
correlate it to a specific frequency reading, connect
a vacuum gauge to a source of manifold vacuum
on the engine, or tee the gauge into the MAP
sensor hose.


5. Turn the ignition ON and note the initial reading.
The reading on the tachometer should be about
454 to 464 at sea level, which corresponds to a
frequency output of 152 to 155 Hz.

6. Start the engine and check the reading again.
If the MAP sensor is functioning properly, the
reading should drop to about 290 to 330 on the
tachometer, which corresponds to a frequency
output of about 93 to 98 Hz. No change would
indicate a defective sensor or leaky or plugged
vacuum hose.
/

 

Subford, thanks again for all the great info.

My multimeter measures Hz so I never thought about using the timing light. I need the vac gauge anyways so I can get to the bottom of this. If anyone cares to make a guess at what the underlying problem is, I will update this post on Fri/Sat with whatever I find.