Surging at Idle/Rough Idle

usa591 · **Posted:** Wed Apr 26, 2017 12:42 am

Hi Team,

I am experiencing a condition where the vehicle surges at idle--not a show-stopper, but bad enough that the lights flicker. This has increased in the last two weeks from what I would consider a "slightly rough" idle that started about six months ago.

First thing I checked was the primer pump. Sure enough, it was soft so I purged the air and hardened it up. Now I'm doing this every other day in order to make the engine run smooth and I only commute about 6 miles each way.

I'm going to install a lift pump--parts on order....but where's the air coming from all of a sudden.

Any other ideas?

I'm still suspicious of my transmission, and thinking that it's time for me to pay attention to it based on this sound: viewtopic.php?t=85369.

flash7210 · **Posted:** Wed Apr 26, 2017 12:49 am

Air can get into the fuel line two ways.
1. melted fuel heater plug in the filter head
2. plastic fuel lines back at the tank

Lift pump is a good idea and will make fuel line leaks more obvious.

I suspect that the flickering lights is because of a bad voltage regulator but get the air in fuel problem fixed first.

usa591 · **Posted:** Tue Jun 13, 2017 2:55 am

Hi All,

So, even after lift pump has been installed, I'm still experiencing the same issue with a rough idle. The weird part is that it only occurs after the vehicle has been warmed up--it purrs like a sleeping kitten when I start it in the morning. Is this a case of dirty injectors?

Here you can see/hear it and watch as my lights flicker here:

https://youtu.be/UU3duRbwlZA

This is an enhanced audio perspective from inside:

https://youtu.be/YCf0CHl49Dw

Pertinent Info:
• Runs great at any other speed other than idle.
• "Chirping" Sounding coming from alternator when it chugs like this--research indicates it's a pulley needing replacing.
• Added Cummins in-tank lift pump--I feel like it idles smoother, but I still have the stumbling on warm up.
• Added 5 ounces of SeaFoam to approximately 5 gallons in tank along with their suggested "hot soak" treatment--no change.
• RPM's are 756-760 according the EngineLink App.
• Ambient air temps are around 70-80 degrees.
• I cleaned the MAP sensor--very little fouling due to ProVent. No change.

Referencing this thread:
viewtopic.php?f=5&t=86614
...I jiggled the wires under the injectors (no change) and also disconnected each injectors' electrical connection one at a time in order to see if one was "worse" than the other: no change other than the engine really started to stumble when I did that.

What gives?!?! :furious:

GordnadoCRD · **Posted:** Tue Jun 13, 2017 4:56 am

I can't make out exactly what it is, but that doesn't sound like a combustion event to me, except for the possibility of an injector leaking out the tip, but you would likely be able to smell the unburned fuel in the exhaust.

Just guessing here, but have you checked your motor mounts? I know it sounds ridiculous, but bad motor mounts can make really unexpected noises, and combined with a bad alternator pulley, might sound something like that.

flash7210 · **Posted:** Tue Jun 13, 2017 7:40 am

Get the engine warmed up to where its doing the weird thing.
Stop the engine and remove the serpentine belt.
Start it up again to see if the weirdness goes away.

What Im hearing in the videos doesnt seem like a engine problem.

The lights flickering is because of the alternator.

usa591 · **Posted:** Tue Jun 13, 2017 11:11 am

GordnadoCRD wrote:

Just guessing here, but have you checked your motor mounts? I know it sounds ridiculous, but bad motor mounts can make really unexpected noises, and combined with a bad alternator pulley, might sound something like that.

Yup, engine mounts have been changed within the last 5K miles.

DieselJeepLuvr · **Posted:** Tue Jun 13, 2017 12:17 pm

I don't hear an idle problem in your video like I was having. Your's sounds like your alternator is going bad and is cycling on and off. While it's running and parked try unhooking the ground on your battery and see if the engine stalls. if your idle IS being dragged down it could be a failing torque converter or flexplate.

usa591 · **Posted:** Tue Jun 13, 2017 2:46 pm

DieselJeepLuvr wrote:

While it's running and parked try unhooking the ground on your battery and see if the engine stalls.

Dum question: Is there a risk of frying something on the Alternator by doing this? What's going to happen to that current if suddenly the circuit is open? Sorry--my layman's mind trying to figure this one out. Also--what will this tell me by pulling the negative and the engine stalls out?

DieselJeepLuvr wrote:

if your idle IS being dragged down it could be a failing torque converter or flexplate.

Yeah, I somehow keep coming back to this due to this other sound I'm having:

viewtopic.php?f=5&t=85369

...any way to diagnose a bad TC other than just replacing it? I do have the intermittent valve drain-back shudder issue and I can certainly make it shudder if I apply WOT around 1700 rpms, but otherwise things feel fine down there.

WWDiesel · **Posted:** Tue Jun 13, 2017 4:13 pm

You should NEVER EVER take the battery out of electrical system on a modern vehicle's charging circuit that contains sensitive electronic equipment! :roll:

Voltage levels can spike to dangerously high levels and do untold damage to sensitive electronic components.
The alternator will see the loss of the battery voltage as super dead battery and output will go to maximum current output trying to bring battery voltage back to normal until the alternator self-destructs.
Electronic components do not like a sudden loss of stable battery voltage taken away from them all of a sudden!

:SOMBRERO:

Bushman5 · **Joined:** Sat Jul 11, 2015 11:05 am **Posts:** 276

Id dump a whole botle of Diesel Kleen (grey bottle) into the tank and run it down the freeway. Cured my "miss" that i had. Now i put it in every tank, or sometimes Redline diesel additive when on sale

GordnadoCRD · **Posted:** Wed Jun 14, 2017 12:53 am

The timing random-ness of the noise made me think of Torque Converter as well, but Usually that's accompanied by a 'whack' or 'clank' type of noise. Perhaps you have that, and it didn't come through my speakers.

40+ years ago, disconnecting the battery was a way to determine if the alternator had output. If the engine died, the alternator was bad.

WWDiesel is correct though, on newer vehicles with computer controls. Good rule of thumb - If there is an OBDII port, don't do it (unless you are intimately familiar with your vehicle and know that it's ok).

DieselJeepLuvr · **Posted:** Wed Jun 14, 2017 12:56 am

WWDiesel wrote:

You should NEVER EVER take the battery out of electrical system on a modern vehicle's charging circuit that contains sensitive electronic equipment!

You're probably right. Old school thinking...

I'd take the alternator in and have it tested. As for the TC / flexplate I'd take to a good tranny shop for inspection. My tranny went from perfectly fine to total failure in 0.4 seconds but it started not wanting to shift into OD off and slow takeoffs on cold starts.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The voltage regulator is built inside the alternator on the KJ CRD. It could be failing and leading to the instability due to torque pulsations. Check the voltage output with and without the instability for verification.

usa591 · **Posted:** Wed Jun 14, 2017 11:30 am

GordnadoCRD wrote:

The timing random-ness of the noise made me think of Torque Converter as well, but Usually that's accompanied by a 'whack' or 'clank' type of noise. Perhaps you have that, and it didn't come through my speakers.

Not hearing any whacking or clanking. FWIW, when I'm experiencing this condition, I'll put it in neutral and it still continues. To my mind, this means that it isn't the TC dragging the rest of the engine down...right?

Thanks for everyone's help weighing in on this, by the way.

This weekend I'm going to try removing the serpentine belt and see what happens.

I'll be checking the alternator output today and report back.

usa591 · **Posted:** Wed Jun 14, 2017 2:23 pm

GreenDieselEngineering wrote:

Check the voltage output with and without the instability for verification.

Right around the 20 minute mark of driving, it starting pulsing again. I checked the output from the alternator with my meter and I'm seeing is dance from 12.36 to 14.22 as it chugs along.

When I tested it after a cold start this morning, it was an even 14.20

As it was sputtering just now, I was hearing a chirp and a slight grinding sound emanating from the alternator pulley whenever it would stumble. Hmmm...that's new. I'm thinking the clutch for the pulley is going bad? Putting strain on the idling engine from mechanical binding of some sort? This alternator is relatively new, replaced it 7K miles ago when I did the timing belt.

mass-hole · **Posted:** Wed Jun 14, 2017 2:37 pm

usa591 wrote:

GreenDieselEngineering wrote:

Check the voltage output with and without the instability for verification.

Right around the 20 minute mark of driving, it starting pulsing again. I checked the output from the alternator with my meter and I'm seeing is dance from 12.36 to 14.22 as it chugs along.

When I tested it after a cold start this morning, it was an even 14.20

As it was sputtering just now, I was hearing a chirp and a slight grinding sound emanating from the alternator pulley whenever it would stumble. Hmmm...that's new. I'm thinking the clutch for the pulley is going bad? Putting strain on the idling engine from mechanical binding of some sort? This alternator is relatively new, replaced it 7K miles ago when I did the timing belt.

If you can check your engine load with your app at idle with everything off(HVAC lights etc) this may clue you in. I think mine idles at around 15% load when warm.

flash7210 · **Posted:** Wed Jun 14, 2017 6:18 pm

usa591 wrote:

GreenDieselEngineering wrote:

Check the voltage output with and without the instability for verification.

Right around the 20 minute mark of driving, it starting pulsing again. I checked the output from the alternator with my meter and I'm seeing is dance from 12.36 to 14.22 as it chugs along.

When I tested it after a cold start this morning, it was an even 14.20

As it was sputtering just now, I was hearing a chirp and a slight grinding sound emanating from the alternator pulley whenever it would stumble. Hmmm...that's new. I'm thinking the clutch for the pulley is going bad? Putting strain on the idling engine from mechanical binding of some sort? This alternator is relatively new, replaced it 7K miles ago when I did the timing belt.

Your voltage should be a steady 14.2 volts.
I suspect you have a bad voltage regulator.
The voltage regulator can be replaced separately. Ive done it.
But its easiest to just replace the whole thing.

usa591 · **Posted:** Thu Jul 06, 2017 2:02 pm

Hi Team,

It was a bad #2 injector.

So I took the CRD to Bud's Diesel in Westminster, CA and they diagnosed & replaced it. $700. Problem fixed...mostly.

The idle still isn't perfect, but it's 90% better. So basically the potential lifespan of these things are 98K miles or 11 years...

When the idle starts getting bad again, I'll be taking it back to those guys--too bad for me they're not closer to Los Angeles proper!

flash7210 · **Posted:** Thu Jul 06, 2017 7:36 pm

usa591 wrote:

So basically the potential lifespan of these things are 98K miles or 11 years...

Consistently run good clean fuel through them and they will last a lot longer than that.

Ive got over 200,000 miles on my factory original injectors.

WWDiesel · **Posted:** Thu Jul 06, 2017 8:00 pm

Secondary 2 micron fuel filter = clean fuel to CP3 and injectors!
Marvel Mystery Oil in the engine oil and in the fuel tank along with some 2 cycle oil in the fuel tank keeps everything well lubricated and happy!!!

Several members on here keep expounding some of the little tricks you can do to ensure long life of these engines and their components....
:roll:

Surging at Idle/Rough Idle

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