This is a long story but I'll try to keep it short as possible.

2003 f350 dually. Fully bulletproofed about 10k miles ago. Everything was running great for about 5k miles. A friend of mine got stuck and I went to pull him out. Got him out but got on it really hard...never overheated or anything.

Next day truck throws a cyLinder 5 contribution balance code. Ran ok but idled rough. Pulled injector and put a used one from a running truck in it. Code went away and runing fine for a few weeks. Took a long trip from FL to Texas, and on the way home same code occurred but idle was not as bad. I would clear the code and it would be fine for a few hundred miles, then would show up again. Made it home, still was driving around town a little with the code only showing sometimes. A couple blocks away from home taking off from a stop sign lost all power and motor shut off. Turned out the Injector o ring blew and hydrolocked the motor.

So now, ordered all new 155cc30% injectors , 58v ficm and new oem injector harness. Installed and Drove the truck to Illinois. After about 700 miles I noticed a little rough idle and had a cylinder 4 cont code. Made to Illinois and back to fl. At fl line I had cyld. 4 and 5 codes now. Cleared and cyld 4 was gone but 5 stayed. Got home and balance test showed 4 and 5 bad injectors. Sent them off to be fixed just got them back in. Truck started fine, smooth idle, ran for about 10 miles and cyld 5 code come back and so does the rough idle. I'm at a loss now.

Will be doing compression test tomorrow. Other than a rough idle truck runs flawless, will roast the tires and pull anything hooked to it. No hot starts, no symptoms of anything else. Possibly a problem with the oil rail feed on that cylinder? Main ficm harness? Bent pushrod? Need ideas

 

Do you monitor or have you tested fuel pressure?

 

I had a similar problem - came across yours as I was researching.

In my case it was misfire on #5 immediately after doing a head gasket replacement and Bullet Proof oil cooler and other things.

The Buzz test passed, swapped injectors and problem stayed on Cylinder #5, tested FICM, FICM harness, etc. Then someone (Ron from DieselTechRon) suggested a compression test. I don't have a diesel compressor tester so I pulled out my leak down tester. Near perfect (

 

Have not tested fuel pressure yet but wouldn't it be more than one cylinder if it was a fuel pressure issue?

 

I had a #5 contribution code. Repaired the FICM and replaced the #5 injector. Code cleared. Now I have codes on #8 and an intermittent code on #3. Tested my fuel pressure and got 45 at idle but way down to 25 or so under load. Going to do the blue spring update this week. I am not throwing any other codes. Have not checked the injection harness yet, but I don't think that is it as the code went away by changing the #5 injector. I believe my injectors are failing due to low fuel pressure.

 

Another thing I'll check then

 

Check your injector harness and connectors. How is your charging system and batteries?

Have the batteries tested along with your alternator. I had a bad battery. Replaced it and my KAM and #5 contribution code went away.

 

Completed the blue spring update yesterday. PSI now close to 70 at idle and never drops below 60 under load. Cleared the codes and the #8 cylinder contribution code did not come back after an hour drive. I'm hoping that did it. Truck seems to running fine now.