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6.0 Driver
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Discussion Starter · #1 ·
I am stumped. I purchased an 04 6.0 4x4 Excursion with 125,000 miles about three months ago. I drove it a couple thousand miles loving every minute of it. Plenty of power and rode like a dream. I bought it with a P0401 (EGR Flow Insufficient) code which according to my research didn’t seem to bother anybody and didn’t seem to hurt my performance.

Background: My problems started a few weeks ago when I drove it to town where I made about 4 stops in about 2 ½ hours. After my last stop, it started fine, but I thought I noticed a slight change in the sound of the idle. That was confirmed when it had a noticeable lack of power on the trip home. A check of the codes showed new B1318 (Battery Voltage Low) and P0275 (Cylinder 5 Contribution/Balance) codes. To make a long story short, I tried some Hot Shots Diesel Extreme in the tank, cleaned battery/alternator contacts to restore alternator output, and changed the oil with Rotella T6 synthetic. I had debated about using the 5W-40 oil with the warm Gulf Coast climate I am in, but decided to try it. I wasn’t impressed because I felt that it started a little slower (but not hard) after the oil change. The two offending codes went away, and after about a week the engine seemed to be back pretty much to normal (although I kind of think it may still have a little less power than before, but it might just be my imagination).

Current Problem: A couple weeks ago, I decided to change the fuel filters (with Motorcraft) before a trip because I had no idea the last time they were changed. The cap on the upper filter was quite tight and cracked in the process of removing it. On a time budget, I replaced it with a Dorman replacement cap from the auto store and used the recommended torque on both caps. Even though I cycled the fuel pump the recommended 6 times, I still had to crank it about 4-5 times before it started. It idled smoothly, but on my test drive it seemed to ride a little rough. On closer inspection I realized that I had a leak around the fuel pressure regulator. It was small, so I don’t know if it was there before or if my attempts to take off the broken cap loosened the dry gasket. I decided not to drive it until I replaced the fuel pressure regulator in case the leak was causing the problems by letting some air in the fuel (didn’t really make sense to me but I didn’t want any problems on the trip). I also noticed that the alternator was under-performing again.

Now I have a DB Electrical 200 Amp alternator, a Sinister Diesel blue spring upgrade adjustable fuel pressure regulator (set to about 62 psi), an ISSPRO EV2 Fuel Pressure Gauge (to give me a little peace of mind), and no fuel leaks.

Here is where I am at after all of that. It still starts and runs fine, but I notice a slight vibration at lower speeds that nearly goes away from 50-60 mph, but that comes back with a vengeance 60-75 mph and lessens over 75 mph. I am sorry for the long post, but I wanted to detail everything I have gone through so far in case I am missing a connection that should be made. It feels like just changing the fuel filters caused this very noticeable vibration. That doesn’t make sense to me, but I am new to the 6.0. Any ideas?
Thanks
 

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While vibration can be an issue with a rough running engine, that typically (in my experience) is either a there or not there thing. With vibrations that change with speed, I would look at driveline. Start with the easy....have the tires checked for balance. If they are fine, check out/change the u-joints. If you have 125K on the clock, they're probably due for replacement.
 

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6.0 Driver
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Discussion Starter · #3 ·
I was thinking the same thing. To me it felt like the front passenger tire was out of balance or something, but it seemed like an odd coincidence that it suddenly showed up with the changing of the fuel filters.

I was actually under it looking at the u-joints this evening to see if there was anything obvious, but then I confirmed it is an engine vibration when I started it up and slowly revved it up in park. The vibration was subtle, but present at low RPM, but became more obvious 1,500-2,000 RPM and seemed to level off a bit over that.

I also discovered that it threw another code: P0472 (Exhaust Pressure Sensor Low Input). I did a quick search for that code and found where a plugged or bad EBP sensor was causing some turbo problems. I will look at that tomorrow. I wonder if I bumped the sensor wires when removing or installing the air cleaner during the fuel pressure regulator upgrade.
 

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If you were able to verify the vibration is there while in park and you're not getting any other codes, I would suspect an injector issue. Yes, definitely check out the EBP sensor because of the code, but I'm not sure it would cause a vibration issue. Usually that would just cause some wonky fuel mixtures and VGT angles. Personally, I'd start it up, verify the vibration is there, and start unplugging injectors one at a time. My gut feeling is when a perfectly fine injector is unplugged your engine will run even worse, but when a certain injector is unplugged you will notice little to no difference. If that's the case, you probably need a new injector....I would check resistance on the coils just to be sure. If, however, you don't notice any difference, it's time to start considering other possibilities. Speaking of which, did you thoroughly drain your water separator? Do you have a fuel pressure gauge? Have you checked for bubbles in your secondary...both from the pump and from the cylinders? Also, I didn't read it, so I don't know, but did you take care of the EGR issue or did the code just go away? A leaking EGR valve could contribute and, along with other factors, might be able to cause this.
 

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6.0 Driver
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Discussion Starter · #5 ·
I've had a couple of busy days so I haven't spent as much time with this as I would like, but I did clean the EBP sensor and tube. It did clear the code, but I probably could have just unplugged it and plugged it back in since the code seemed to be primarily electrical. Clearing that code didn't seem to make any difference on performance.

I had a little bit of time to start investigating the injectors. I did a buzz test and a bubble test both of which checked out fine. I did unplug the #5 injector to see if there was a difference just because of the contribution code I got on it several weeks ago. It had an obvious impact on performance. I didn't have time to unplug the others, but the even side looks pretty daunting to try that anyway. Is there an easy way? It looks like I would have to pull the entire air intake assembly out of the way to get to the plugs. I don't really think that unplugging the injectors would tell me much anyway since the engine is running fairly smoothly at idle. It doesn't even sound that bad when it is vibrating noticeably. If it is an injector issue, it is subtle enough that I would think that it should run worse even if the bad injector were unplugged.

As for the other items you mentioned, I did drain the water separator when I changed the fuel filters (not much water there). I even did it a second time when I re-checked to make sure there wasn't any issues with the way I had installed the cap. I did install a fuel pressure gauge before I changed out the fuel pressure regulator. I wanted to be able to see the before and after pressure. Before I changed the regulator, the pressure was at 50 psi. Now it is sitting at about 62 psi at idle.
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I haven't done anything with the P0401 EGR code. It had that since the time I got the truck and it didn't seem to affect the performance. It is my understanding that code basically means that the EGR valve isn't opening at all. I have seen posts where some guys said their trucks ran better with that code. I had originally pulled the valve and replaced the o-rings just to make sure it wasn't leaking around the rings. It worked fine mechanically--I just assumed that electrical side of it was shot and wasn't opening. I also unplugged the valve and it ran the same as when it was plugged in. Since it was running fine, I wasn't too worried about replacing it and since I had driven more that two thousand miles without the code causing problems, I didn't figure that it would suddenly make it start running like this.

Thanks for all your suggestions.
 

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It can be a pain to get to the other side's injectors, but if you loosen the degas bottle and use a long screwdriver to depress the clips, it's not bad at all.

If it's that subtle you're right, you may not be able to detect it by unplugging an injector. I had thought it was more pronounced. My only other thought at this point is to find someone with the capability to do some deep diagnostics such as a contribution test, or maybe do a compression test to see if you have a cylinder which is going to be making less power than the others. Hopefully someone else might have a good idea and will chime in.
 

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6.0 Driver
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Discussion Starter · #7 ·
Yeah, the engine really isn't running rough. It is just that it gets a bit of a vibration when it is reving up. It is there but not that obvious at lower RPMs, but it gets more pronounced 1500-2000 RPM and levels off a bit over that. Even at the stronger vibrations, the engine doesn't sound horrible or smoke though.

I was hoping there would be a simple fix related to something that happened during my fuel filter and regulator change since that is when the problem showed up. If I can't find something obvious over the weekend, I will probably take it to the local diesel shop next week.

For a shot in the dark, I did try to vary my fuel pressure on the Sinister Diesel adjustable fuel pressure regulator I installed--just to see if it had any impact since that was the other thing I changed. But then I noticed that it started leaking fuel around the adjustment screw. I may have just loosened it too much in making the adjustment--but just one more thing to chase down.
 

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Well, I have to ask.
Did you ever replace the fuel filter caps with motorcraft ones?
What oil filter and cap are you running?
3rdly, you couldn't pay me to run ro-####-a. Especially when a cheaper $10/gal oil runs better than that crap.....
With the P0401, have you actually looked to see if you have a egr valve and if its plugged in? Might remove it and clean it.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

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i too suspect an injector,
do you have a trailer to pull? get it under a load , keeping it steady- do you then get a more pronounced vibration?
a long hill might do the same.
 
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