Occasional slight stumble on idle and few more engine turns to start

[Blakers]

Most of the time my truck runs just fine. Good power. Will smoke when I get on it hard. And idles nice and smooth.



But occasionally it takes a few more revolutions of the engine before it will start. I also notice that sometimes it will have a slight stumble while idling - not a whole cylinder missing, but just enough of a stumble to shake the truck slightly and aggravate me while filling out paperwork, etc. I got out and listened to the exhaust and could hear the stumble back there as well. (A/C was off) Not sure if the stumble and harder starting are related or not. I can drive it down the road a bit and then the idle is fine.



Another thing I notice is the tone of the exhaust changes when the A/C kicks on and off while the engine is idling - almost sounds like a stumble, but I have been contributing it to the change in load on the engine.



My truck has about 105,000 miles and it's run all day 5 days a week for about 100 miles a day stop and go on back roads and off road.



Thanks.

 

[TCDiesel]

You are welcome to try our test sensors, Pressure,LV,Fca,just need to pay the $5. 00 shipping costs. I would eliminate these 1st,before moving on to Pump (lift/Cp3) and Injectors.

 

[Blakers]

You are welcome to try our test sensors, Pressure,LV,Fca,just need to pay the $5. 00 shipping costs. I would eliminate these 1st,before moving on to Pump (lift/Cp3) and Injectors.

I think I'll take you up on that. How long does it generally take to check things out? Just wondering, so I'll set some time aside so I don't tie up your equipment for long.



Blake

 

[Blakers]

I forget to mention that I have a van Aaken SmartBox™ C3. 2 which has worked flawlessly since I installed it in 2003.

I haven't noticed any stumbling at idle lately. Only a slight change in exhaust tone now and then at idle. Otherwise, it's been running and starting good.

 

[TCDiesel]

I think I'll take you up on that. How long does it generally take to check things out? Just wondering, so I'll set some time aside so I don't tie up your equipment for long.



Blake

Need to contact Me via phone if still interested in the Test sensors?

 

[Blakers]

I thought it was gone, but now the miss at idle is back. Smooths right out under load. Has anyone had this problem?

 

[Wingate]

my 06 model does the what you are describing from time to time... . I feel like when the a/c compressor is cycling on and off, the load is momentarily changing on the engine, all the while, its trying to maintain 0% throttle position and a constant idle speed.

From time to time, it seems that I have to twist it just a slight bit longer before it fires up. . Haven't decided what thats caused form yet, but my B-I-L borrowed my truck several times... . I told him NOT to worry about putting fuel in it, but he did anyway...

(I did NOt want him putting fuel in it due to him shopping by price, not by whats best for my truck! Theres no telling what he put in it. . !!!) Also, on this same fuel filter, I had to purchase some B blended fuel while up in the Dallas area... Its just about due for a filter change, so I am withholding judgement unit I replace the filter... .

Other than that, great power, no abnormal noises or smoke... . Truck is stock with 37K miles on it. .

 

[C.Solomon]

My 06 has done the same thing. Last winter it would do it almost everyday, now this summer I haven't noticed it at all.
I do still have the occasional longer then normal start time.
I to wonder what causes it.

 

[JJPage]

Talking about this on another post, could it be the grid heaters cycling, causing the stumble because of weak batteries? I know my lights dim when they cycle, I'm still on my original batteries, maybe time to replace.

 

[Blakers]

Talking about this on another post, could it be the grid heaters cycling, causing the stumble because of weak batteries? I know my lights dim when they cycle, I'm still on my original batteries, maybe time to replace.

On mine it can not be the grid heaters because it does it later in the day, after it has been running for several hours.

 

[Wingate]

Mine either... My truck will do it after being ran for several hourts on a 100 degree day. Batteries are less than 1 month old.

After thinking about this for a minute, I wonder if the Cummins software logic is similar to Cat logic. . On most Cats, there is a speed/timing sensor that looks for a reference signal from a wheel being driven off the camshaft. If the engine shuts down just past #1 TDC, then on startup, the crankshaft will have to spin two complete revolutions before the ECM will arm the injection pump and start attempting to fire the injectors.

This might explain why my truck only seems to take that little extra twisting on some occasions, but not others... . ???????

 

[Blakers]

I didn't notice this stumbling problem for several months, but a couple days ago I started it in the morning and it was only firing on 5 cylinders. After about 4 or 5 minutes, the other cylinder came in and it was ok. It was about 20 deg F out and the truck was plugged in during the night.

Every now and then it goes into a stumble for a few minutes while idling during the day.

Blake

 

[cerberusiam]

Sounds like you have an injector solenoid going bad and intermittently not firing.

 

[barryg41]

My truck stubbled for years until I had James Northum of Dallas put in a new DTT transmission. He also installed the noise suppressor, and at that time he told me to wrap the ground cable coming from behind the altenator to the passenger side battery with tin foil. Then wrap black tape around it to keep it secure.



No stubble since. This worked for me!



Can worn out brushes on an alternator cause more electrical noise than say a normal or new alternator?

 

[Blakers]

Sounds like you have an injector solenoid going bad and intermittently not firing.

How common is this?

 

[Blakers]

Need to contact Me via phone if still interested in the Test sensors?

I'll give you guys a call. Been putting it off because it's only occasional and now I'm waiting for better weather to work on it.

 

[Blakers]

My truck stubbled for years until I had James Northum of Dallas put in a new DTT transmission. He also installed the noise suppressor, and at that time he told me to wrap the ground cable coming from behind the altenator to the passenger side battery with tin foil. Then wrap black tape around it to keep it secure.



No stubble since. This worked for me!



Can worn out brushes on an alternator cause more electrical noise than say a normal or new alternator?

Do you wrap the foil around the ground or the hot wire to the battery?



I have so much electrical equipment in my truck, I wonder if that is causing anything. I have 2 GPS units, a Spot GPS locator for work, an LEL/CO/H2S/O2 alarm meter, Sirius radio, plus 2 cell phones.



Blake

 

[cerberusiam]

How common is this?

Pretty common as a symptom. The high voltage and multiple events take their toll after a while.

 

[barryg41]

Do you wrap the foil around the ground or the hot wire to the battery?



I have so much electrical equipment in my truck, I wonder if that is causing anything. I have 2 GPS units, a Spot GPS locator for work, an LEL/CO/H2S/O2 alarm meter, Sirius radio, plus 2 cell phones.



Blake

Just the ground. From where the ground comes out the loom to where the ground is secured on the battery tray. I would think the noise supressor took care of most of the interference.



Here's a pic, if it works...