2003 6.0. Miss when hot, P0275

[chadnixon]

A while back I picked up this truck for a project. It ran rough and had a miss when cold, or when in overdrive, but otherwise ran fine once hot. I had it looked at by a friend who is a ford diesel tech. He brought over his lap top and ran cylinder balance test and failed number 5. Also said 3 and 7 were low. Truck was not throwing any codes at the time, and once it was hot seemed to run normal.

I changed all 4 injectors on that bank, 1,3,5,7. I also sent my ficm away to ficmrepair.com and had them fix it as I was getting only 40 volts when cold. While I was inside I also replaced oil cooler and updated fuel pressure spring to the blue spring. New filters and oil all the way around as well. I put it all back together and flashed it up. Ran perfect cold. Once it was hot I noticed a stumble, worse then before, and throwing P0275 for cylinder 5 again. I then suspected FICM harness as the x2 plug was broken and held onto ficm by wire ties. I ordered a new harness and installed. Still have same result. Rough when hot and P0275.

Now this wouldn't be the first time that I have heard of a injector being faulty right out of the box, but what are the odd's it would be number 5 again, the same injector as before.

Any ideas? If I were to venture a guess I would say maybe a slightly longer crank. About the time your brain thinks hey this should of started, it starts.

No other faults other then P0275
FICM voltage at 48 volts at all times

[chadnixon]

A little update.

I just went out and checked my connections again, all good. I decided I would start it back up. Truck is still warm from previous road test. Started and idled normal. Rev-ed it up and it hesitated then returned to rough idle.

I let it sit for about 2 minutes, started, runs fine. Rev-ed it up and hesitated then returned to rough idle. Engine temps are around 140. I am almost inclined to say that it is not temperature related, but only seems to happen after you hit the throttle. It will idle normally for a long time but once you hit the throttle just once it will miss until powered down and restarted.

[npccpartsman]

Most likely a bad injector.

[2003kingranch]

Most likely it is an injector. I dropped #4 injector in my truck a while ago for no reason. It would run great until eot got to 180+ then it would barely run and just dump black smoke. It wouldn't go more then 5mph without the egt's running 1k+. Let it cool down and it was fine. Is there any kind of smoke coming out of the exhaust?


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[chadnixon]

I don't believe its a injector again. Like I said number 1,3,5,7 were just replaced a few days ago because number 5 was weak. The odds of getting a failed injector right out of the box are slim, yes it does happen time to time, but the odds of me getting 1 injector bad out of 4 new ones, then putting the 1 bad one back in the number 5 hole is so slim I just don't buy it yet.

Something else has to be happening here that I am overlooking. If I go out and start the truck it runs great. It will run as smooth as the day it was brand new. I let it run up to full temp, even kicks up on high idle and its still running beautifully. Give the throttle one blip and it rev's up and returns to a "lope" idle and throws number 5 balance. If I shut it off for 30 seconds for the ECM to reset, it works great again until you blip the throttle.

It is in no way related to engine temps at all either. And no smoke from the exhaust. It seems to run fine except the lope idle and you can feel the miss in overdrive. Aside from that it pulls great through throttle range. To me it almost seems like something is going into default mode. Like I said if I start it up right now, its running fine. As I slowly rev it up somewhere around 1200 it changes sounds, then runs rough. shut it off for 30 seconds and all is well again.

[xpbprox]

Maybe just switch the #5 injector out with another one, for example the #1 injector. See what happens.
Not sure if this is related but I had a truck that I was working on, and the the injector harness pigtail had 2 of the 4 connections get pushed in to far so the injector was only connected to 2 of the 4 connections when plugged in. (it through a low circuit code though)

[npccpartsman]

Originally Posted by xpbprox

Maybe just switch the #5 injector out with another one, for example the #1 injector. See what happens.
Not sure if this is related but I had a truck that I was working on, and the the injector harness pigtail had 2 of the 4 connections get pushed in to far so the injector was only connected to 2 of the 4 connections when plugged in. (it through a low circuit code though)

+1.

Also, check the pushrods and valve train. If it's not the injector it's something in the cylinder.


Where did the injectors come from? Are they Motorcraft?

[chadnixon]

I am going to pull the lid and take a look again. I can't see it being anything cylinder or valve train related either. If the PCM commands high idle, it goes up to about 1100 rpm and runs fine. If I go to 1100 rpm with my foot it misses.

It has to be electrical, somewhere.

[FL-F350]

hi man do you find the problem ? i got the same problem