Help 7.3 missing, no codes, did buzz and contribution tests

[Probuilder]

I cleared all codes, reran the tests, KOER and KOEO. This was all done after checking the resistance on all injectors. They all come out the same and with in specs.

These are the new codes that I get with the AE Scanner on my laptop.
P0475
P1280 ICP too low.

Now on the idle I am running a Injection pressure of 481.96 psi and at 2200 rpm it is at 1153.2 psi. Do these numbers sound right?

The truck is the same as before, so no change.

[907DAVE]

Just for giggles try running it with the ICP disconnected......or have you done this already?

[907DAVE]

And just so we are all on the same page here - the truck is missing at idle and under load, correct?

Would you guess it is a steady miss, or more of a random misfire?

There are no more CCT faults?

No actual CEL when running?

[Probuilder]

And just so we are all on the same page here - the truck is missing at idle and under load, correct? correct

Would you guess it is a steady miss, or more of a random misfire? Steady

There are no more CCT faults? none

No actual CEL when running? no light

I will try the CCT with the ICP unplugged when I get back home.

But why is the P0475 code in there?

[907DAVE]

The P0475 indicates an Exhaust Backpressure (EBP) Control performance concern. Monitor the exhaust backpressure reading Key On Engine Off (KOEO) and at idle. This value should be equivalent to atmospheric pressure. A typical reading at sea level would be 14.6-14.8 PSI.

Monitor for an increase under load to see if increases, not to exceed approximately 35 PSI. If no increase is noted, check/replace the sensor and exhaust supply tube for carbon restrictions and recheck for proper operation.

This will not cause your misfire.

If you are feeling really ambitious you can pull both valve covers off and disconnect the injectors, one by one, with the engine running. You are looking for the one that doesn't change the way the engine runs, or has the least effect on it.

Kinda a crude way to do it, but gets the job done.

[Probuilder]

number 8 has almost no change to the engine. But the rest cause the motor to slow down and miss worse. So does that mean that the #8 injector is bad?
Also this truck has 342K on it. Would u just replace q injector or should I change all 8?
Can these injectors be changed out with a set from a 97 motor? I have a spare set of those laying around. So it would be a cheap fix for me. This truck is an early 99, build date of 5/98.

[907DAVE]

Yip, #8 injector bad.

As long as the injector "codes" are the same they are interchangeable.

[SICKS-O]

Originally Posted by Probuilder

number 8 has almost no change to the engine. But the rest cause the motor to slow down and miss worse. So does that mean that the #8 injector is bad?
Also this truck has 342K on it. Would u just replace q injector or should I change all 8?
Can these injectors be changed out with a set from a 97 motor? I have a spare set of those laying around. So it would be a cheap fix for me. This truck is an early 99, build date of 5/98.

do cyl 7 & cyl 8 still give a weak buzz?

the engine not running much different with #8 unplugged is a good clue, but doesnt tell us if the injector is at fault. i would suggest a compression test on that cylinder before going further.

i wouldnt replace anything until you have found the cause of your problem. if you do need an injector or 2 i would only replace whats failed. 8 new injectors are BIG money.

the simple answer is no. those are single shot injectors, unless theyre from a cali model. either way doesnt matter because the flow rating is different, 97-older 7.3 = 90cc injector, 99 = 120cc injector, 99.5+ 130cc injector.

you will need an AB model injector or a long lead injector for cyl 8 (if ford offers one).