My truck runs rough at idle, any throttle position, unloaded, under load, doesn't matter. Now it is NOT a cylinder misfire. However, it does seem to sound consistent when i enable 6 cylinder high idle. You can hear it and feel it in the truck during high idle (you can even see it in the mirrors. I have tried to take a video but it doesn't really show up well because the truck is just so loud. Now in 6 cylinder high idle (at 1200) rpms the "miss" is Consistent but about once every second or so. How can this be?! The whole fuel system seems to check out. Fuel pressure is all normal. Still have great fuel economy and power. There is usually a heavy lope when cold, then clears up when driving. If you listen to my truck from about 100 feet away, you can hear it running strange, like its not firing consistenly. When im cruising going 55 and let off the gas SLIGHTLY (so little load on engine), the truck starts sputtering and can be noticed on tach (+/- 50-100 rpm). And when coming to a stop (no throttle), it will sputter the same way until i get to a complete stop where you can hear the truck lope (SLIGHTLY) at idle. I have taken it to the dealer twice, cummins once, shown two other diesel mechanics...and they are stumped. The ONLY thing I can think of is a new harmonic damper. I ordered an ati damper to see if it helps. I hate to throw a part at it but Im at a loss. If anyone has anything I can work with please help me. I can't drive it till i get this thing fixed. Ill try to get SOMETHING for a video but...

Without turning on the air conditioning compressor turn on everything you can that is electrical. Headlights High beams inside lites Radio etc. And see if the idle goes even more rough.

Are you thinking AC noise or something alternator related (it is the stock alternator...)? There wasn't an ac noise issue a month back when I last checked it.

Edited October 30, 20168 yr by Cumminz

No, not ac noise. I've heard of a rough idle problem from too much load on the electrical system throwing off sensor voltages APPS etc. I don't know except what I have read. The guy had decent fuel pressure but found the fuel pump putting excessive load on the elect. system.

Edited October 30, 20168 yr by JAG1

Mine does this in high idle, part throttle revved up, etc. It only does it with no load though. Through different VP's, injectors, programmers, an entire engine, etc it has always done it. I chalk it up to an angry injection system and live with it. 

Might pop test the injectors if they have any mileage on them. 

 

Mine randomly has a cool down lope after hard runs. So like getting off the interstate running 80 MPH and then stop at a truck stop. When I pull in to park and allow the Quadzilla to do the cooldown you hear a random lope. As it cools it typically goes away.  I've had mine re-tested by Vulcan Performance and there is no issues with the injectors. In my case it falls under...

 

9 hours ago, TFaoro said:

I chalk it up to an angry injection system and live with it. 

The injectors probably have about 300 miles on them. Tried swapping in the old one for shits & giggles and same thing. I can understand if it had just a slight lope but it sounds terrible like skipping at idle. Never used to do this. Compression on cylinders were all above 450. I tried turning on the accessories and even unplugged alternator all together with no difference. Even the guys that couldn't figure it out even said it isn't right, they just don't know what it is. You can see the tach fluctuating at idle, accelerating, coasting to a stop (real evident). When moving the throttle slowly in park under hood, you can hear and see the engine start shaking. 

Edited October 30, 20168 yr by Cumminz

If not electrical got to be fuel. I think you might getting just a small amount of air in the fuel system. Just enough to grab your attention at idle.

What about the top of the tank fuel connection or OEM filter cap not down tight something small air is what it is I'd bet. Factory filter needs 25 ft pds. to be tight. No quick connect fuel lines right?

Does it act the same on full tank of fuel as it does with the tank low? I am thinking fuel myself. Either a restriction or air getting in.

There are lots of places that air can get it. The return line coming out of the back of the cylinder head, the return tee, any and all fuel line connections. The top of the tank and the fuel tank sender basket are also known for problems. One way to check for air leaks is to route in a piece of clear hose into the fuel system. You can watch for air bubbles traveling through the clear hose. Another test you can run is doing a hot wire on the injection pump. This should eliminate any electrical issues as long as the pump itself is in good working order. Check out this link. It has tons of good info on what to check in the fuel system and also the hot wire trick for the pump.

https://www.bluechipdiesel.com/vp44_diagnostics.html

well I installed the new airdog lift pump because of dry rotting lines from my old fass system. So all lines are new as well as connections. No factory fuel filter. Completely bypassed because of airdog. I did the clear hose method just before the vp44 routed up to the windshield. No air at all. I have a new vp44 from midwest fuel injection. Did the hot wire test that is all good. Runs the same with the hot wire test. It has been acting up since the old fass system too so...I think the lift pump isn't sucking air and it has the sump kit so that helps.

 

The dealership performed the "turn off each cylinder" test and each cylinder performed normal  rpm drop. If this helps anything. But this also makes me think that fuel system (which is pretty much all upgraded) may not be the issue. But don't know.

 

Acts the same no matter what fuel level. As well as #1 or #2 diesel, cold or warmed up.

Edited October 30, 20168 yr by Cumminz

Unplug you edge and see if it goes away. 

 

I had an Diablo PP that was making my truck do weird stuff. 

 

Turns out my PP was on the way out. 

Its unhooked now. Does it hooked up or not.

I would like to keep my promise and solve this problem of mine. It won't exactly be solved until tomorrow but updated at least.  Like I said previously I have taken it to Dodge twice, and Cummins once and nothing was done to try to diagnose my truck. My brother and my dad took there trucks to Calibrated Power Solutions in Marengo, IL. for tuning and turbos for there trucks. I took my truck there to see what they can do for my truck. Two hours later they told me the issue was a terminal in the wiring harness that wasn't connecting and should solve my issue. They were going to have a technician take it home overnight to verify it is gone. Waiting for the final results now. When I go to pick it up, Im going to ask which terminal was screwed up and how they found it. Very interesting issue....

I really hope that was the problem.  Mystery gremlins sure are a pita.

There was a article in the TDR mag. of a truck doing like yours after lots of checking resulting Dodge buying the truck back, it turned out that the oil had been overfilled causing the the rods to hit the oil.

I picked up my truck today. Still not fixed.

How long has it done this?  Any relation to when you did ANYTHING to the truck?  And.....did it begin after the install of the new VP?

Going on about a year now. Seems like its getting worse and worse. Before vp44 and Shortly after i bought the truck lol (About a year). Don't drive it too often. I might try messing with the connecting tubes again.

Edited November 25, 20168 yr by Cumminz

6 hours ago, Cumminz said:

Going on about a year now. Seems like its getting worse and worse. Before vp44 and Shortly after i bought the truck lol (About a year). Don't drive it too often. I might try messing with the connecting tubes again.

 

I'm confused.....  So it did this before you bought it "and" after you bought it, or just after?  Because below you mention that "its never done this".  Are you saying it acted even worse after the injector swap?

 

On 10/30/2016 at 6:11 AM, Cumminz said:

The injectors probably have about 300 miles on them. Tried swapping in the old one for shits & giggles and same thing. I can understand if it had just a slight lope but it sounds terrible like skipping at idle. Never used to do this. Compression on cylinders were all above 450. I tried turning on the accessories and even unplugged alternator all together with no difference. Even the guys that couldn't figure it out even said it isn't right, they just don't know what it is. You can see the tach fluctuating at idle, accelerating, coasting to a stop (real evident). When moving the throttle slowly in park under hood, you can hear and see the engine start shaking. 

 

 

On 11/16/2016 at 3:21 AM, Cumminz said:

I would like to keep my promise and solve this problem of mine. It won't exactly be solved until tomorrow but updated at least.  Like I said previously I have taken it to Dodge twice, and Cummins once and nothing was done to try to diagnose my truck. My brother and my dad took there trucks to Calibrated Power Solutions in Marengo, IL. for tuning and turbos for there trucks. I took my truck there to see what they can do for my truck. Two hours later they told me the issue was a terminal in the wiring harness that wasn't connecting and should solve my issue. They were going to have a technician take it home overnight to verify it is gone. Waiting for the final results now. When I go to pick it up, Im going to ask which terminal was screwed up and how they found it. Very interesting issue....

 

Did you ever go back and ask them about this "non connecting wire" in the harness?  Maybe there's something to that and whatever they thought they fixed wasnt actually fixed correctly.....  I'd certainly want to know what they were talking about.

 

On 10/29/2016 at 7:10 PM, Cumminz said:

My truck runs rough at idle, any throttle position, unloaded, under load, doesn't matter. Now it is NOT a cylinder misfire. However, it does seem to sound consistent when i enable 6 cylinder high idle. You can hear it and feel it in the truck during high idle (you can even see it in the mirrors. I have tried to take a video but it doesn't really show up well because the truck is just so loud. Now in 6 cylinder high idle (at 1200) rpms the "miss" is Consistent but about once every second or so. How can this be?! The whole fuel system seems to check out. Fuel pressure is all normal. Still have great fuel economy and power. There is usually a heavy lope when cold, then clears up when driving. If you listen to my truck from about 100 feet away, you can hear it running strange, like its not firing consistenly. When im cruising going 55 and let off the gas SLIGHTLY (so little load on engine), the truck starts sputtering and can be noticed on tach (+/- 50-100 rpm). And when coming to a stop (no throttle), it will sputter the same way until i get to a complete stop where you can hear the truck lope (SLIGHTLY) at idle. I have taken it to the dealer twice, cummins once, shown two other diesel mechanics...and they are stumped. The ONLY thing I can think of is a new harmonic damper. I ordered an ati damper to see if it helps. I hate to throw a part at it but Im at a loss. If anyone has anything I can work with please help me. I can't drive it till i get this thing fixed. Ill try to get SOMETHING for a video but...

 

Did you get the new dampener installed yet?  And why didnt you go with a Fluidampr?  I hear great things about them.

 

Lastly, can you video this vibration or shake?  If its as apparent as you describe then it should easily show up on video.

Edited November 25, 20168 yr by KATOOM

I installed the vp44. It was happening before that. I had the a year before it started having a skip at idle and progressively getting worse. I installed the damper, and no change to the symptoms.