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...

Any chance the VP timing key was partially smashed in the shaft cog?

 

And did you ever go back to that shop and ask them about the wire not making a contact, which they thought they fixed?

 

11 hours ago, KATOOM said:

Any chance the VP timing key was partially smashed in the shaft cog?

 

   So you say there are no codes, fuel system, injection pump, compression and charging system (no A/C noise) are all good along with a new damper installed.  May be the timing is to far advanced all the time.  This could be caused by a faulty electronic signal to the ECM from the load or temp sensor or the ECM itself or a mechanical problem of the cam/injection pump timing. 

  I had a car act like that.  I found that the solenoid for the variable cam timing was sticking and the intake cam timing was always at 22° advanced. 

15 hours ago, Cumminz said:

started having a skip at idle and progressively getting worse

 

Skip at idle is typically more of injector issue than a VP44 issue. This will show more as the engine is hot than cold. I would say pull the injector and have them pop tested.

As much as know the VP mechanical timing being off would cause the idle skip, the reason I'm leaning towards the injectors as the culprit is because 1) it gets worse as the engine warms, and 2) he mentioned that it began running even worse "after" swapping injectors.  So either he's experiencing two problems (smash key and faulty injectors) and we're diagnosing its as one, or he merely had bad injectors in there before and swapped them out for worse ones.

Is there any easy way to check the timing key? Just pull the pump gear off? I am still wondering about mine being off that way too. I was thinking about checking it just for the piece of mind.

 

As for the OP, it may be worth sending the injectors for a pop/flow test just to rule them out for sure. Also, while that is happening you can check/replace the connecting tubes if needed. Couldnt hurt just to check.

23 minutes ago, Ilikeoldfords said:

Is there any easy way to check the timing key? Just pull the pump gear off? I am still wondering about mine being off that way too. I was thinking about checking it just for the piece of mind.

 

As for the OP, it may be worth sending the injectors for a pop/flow test just to rule them out for sure. Also, while that is happening you can check/replace the connecting tubes if needed. Couldnt hurt just to check.

 

You can take off the shaft nut on the timing gear and then using a puller, pop the gear loose from the shaft.  The gear wont come off but with a mirror and a bright flashlight you can wiggle the gear forward and loose on the shaft and peer down to see if the key looks normal.  Its not "easy" to see in there but at least you can get an idea.

Edited November 27, 20168 yr by KATOOM

Is there any way that gear could get off a tooth? Asking for both me and the OP. Or is that gear pretty fool proof to pull off and put back on? Sorry, just never had to do one myself.

If his gear was off a tooth would that cause the problems he is experiencing? Kind of like an old school distributor being off a tooth on an old v8. It will still run just miss and run rough...

It doesn't come off but merely pops loose, so there's no way to be off a tooth unless it was installed that way.  The nut torques back on at 125 lbs too.

I HAVE A QUESTION? So "hot wiring" the vp44 just gives the fuel solenoid power correct? It is still a mechanical pump right? how does it idle? Where is the connection between injection pump and cam sensor? (I don't have a crank sensor so...not really relevant anyway? So When it is hot wired and it still idles bad, am i looking at a bad cam sensor circuit or something mechanical somewhere that is still causing this? When I was on the phone with a cummins buddy he said to change cam sensor (which i did with new oem cummins one) which didn't help. I still see the fluctuations in rpms throughout rpm range...and sounds terrible through exhaust. But my exhaust is too loud to capture the roughness on camera with my phone.

Edited December 2, 20168 yr by Cumminz

The VP has its own internal timing/positioning sensor which runs off the shaft.  So if the shaft is out of position then the VP will be out of time as well.

I have an update. I redid the "hot wire" test and it ran smooth like it should. Plugged the vp44 back in and started having rpm fluctuations. I got it on video. So this is sounding like a wiring issue. where should i look now?!!! This is so frustrating. Does this sound like a wiring issue? I literally cleaned every ground on the truck i could find. Clean all the big plugs. what circuits should i look for? Could the CAN bus cause this? Where is that even at? Oh and I plugged in a good used ECM and it was the same. So fuel and computer is good.

Edited December 3, 20168 yr by Cumminz

1 hour ago, Cumminz said:

I have an update. I redid the "hot wire" test and it ran smooth like it should. Plugged the vp44 back in and started having rpm fluctuations. I got it on video. So this is sounding like a wiring issue. where should i look now?!!! This is so frustrating. Does this sound like a wiring issue? I literally cleaned every ground on the truck i could find. Clean all the big plugs. what circuits should i look for? Could the CAN bus cause this? Where is that even at? Oh and I plugged in a good used ECM and it was the same. So fuel and computer is good.

Can you upload the video so we can see what it's doing?

Yeah...about that....The file size is too big. Ill have to compress the files somehow. There are only a couple minutes long. Standby...lol

33 minutes ago, Cumminz said:

Yeah...about that....The file size is too big. Ill have to compress the files somehow. There are only a couple minutes long. Standby...lol

Upload it to YouTube, then drop the link here  

The first video shows the pump hot wired. Second video is with it plugged in. The check engine light was from hot wiring. No codes.

IMG_1127.m4v

IMG_1128.m4v

The differences in exhaust aren't real noticeable in the videos but the rpms are the important thing. I wanted to tighten the terminals on the vp44 plug and ecm plug but it seems that you can't take either apart to get to the terminals.

Edited December 4, 20168 yr by Cumminz

10 minutes ago, Cumminz said:

The first video shows the pump hot wired. Second video is with it plugged in. The check engine light was from hot wiring. No codes.

IMG_1127.m4v

IMG_1128.m4v

I've never seen a 24v tack sit steady (like your first video.) Mine has that little bounce all the time, and acts just like yours. I really am not seeing a problem

Does it make your exhaust sound like ****, makes your truck shake when holding the throttle? It never used to do this.

2 minutes ago, Cumminz said:

Does it make your exhaust sound like ****, makes your truck shake when holding the throttle? It never used to do this.

Yes. I THINK mine started doing it when I put larger injectors in, but I'm not positive. 

I'm not sure if you were here when I ripped mine apart, but I completely rebuilt the motor, redid all wiring harnesses, new VP, 3 sets of injectors, new crossover tubes, checked for air in the fuel supply,  and on and on... Still does it to this day, but it runs fine so I chalked it up to an angry injection system. If you'd like me to take a video just let me know.

Mine has a 25-50 RPM fluctuation ever since I bought it. There were a lot of guys talking about having that over on the Cummins forum years ago. (Talking about when the grid heaters discontinue too).

 

I did note that your voltage gauge read lower charging volts on the second video.

 

Do you have the Timbo APPS and running 2 cycle oil? I ask cause mine sounds a bit more quiet than yours.

Edited December 4, 20168 yr by JAG1

I have the timbos apps and was not running 2 cycle oil here. But in the first video it ran much smoother and quieter.