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

[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]

are 7 and 8 still giving a weak buzz? i would also do a compression test on cyl 8.

[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).

[Probuilder]

Ok so you are saying that it maybe the compression and not the injector? Even though the buzz is very dull in sound, on the buzz test?
I will try to find someone that has a compression tester for these trucks.
I have just about had it with this truck, I am looking for a 7.3L that is newer so that I get more info from the scanner, than I do with the E99 systems.

[88Racing]

Is this resolved?

[cleatus12r]

I had left a bit of a resolution on the service ticket that Troy started, but have yet to hear back about it. If you can leave this thread open for a bit, I'd like to hear back from him myself.

[Probuilder]

Cody,
I have replaced the #7 and #8 injectors, but to no avail, I still have the problem. It don't seem to be as prominent, but still has the miss. I am in the process of going back through every check that everyone suggested prior to replacing the injectors. Does anyone know what this motor should have for compression, and what is acceptable?
I am about ready to buy a bow tie, if I cant figure this out.

[Power Hungry]

We need to get you down here for a weekend and see what's going on with your truck.