Engine/Transmission (1998.5 - 2002) Need help with stutter at idle--Video inside

[firefighter_2000]

For quite some time, my truck has had a stutter at idle. Its like the motor stops for a split second and is right back to normal. Truck runs great otherwise on the road. Have good fuel pressure from the lift pump (replaced about two months ago). Have new injectors as of about 4 months ago (rv275). But the stutter is still there. The only thing I can think of left, is the injection pump. No codes are found either. The injection pump has about 50-60k miles on it. Its done it for about the last 20-30k miles. I took a video at the tailpipe this morning. If you listen closely you can hear the stutter.



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[AStrand]

That is strange. Haven't heard that before.

 

[JLandry]

It almost sounds to me like one of the injectors might be partially cutting out. I've used a DRBIII to selectively turn off fuel injectors on my engine and it sounds somewhat similar but more pronounced. But since you replaced the injectors, they shouldn't be the problem.



Maybe you should try hot wiring the VP44 and starting the engine (after the engine is first warmed up normally) to see if the problem still occurs. If it did you could rule out anything related to the ECM or wiring harness. Hot wiring instructions can be found HERE.



Good luck,



John L.

 

[ALepley]

Definately sounds fuel related like it is getting ready to stall out from lack fuel. That is a strange noise indeed.

 

[firefighter_2000]

none

Its wierd because it doesnt always do it. It will also sometimes do it when the truck is coasting, and the engine has returned to idle RPMs. I put in new injectors, and a new lift pump thinking one of these was the problem. It never does it when the truck is over about 1000 RPMs. In fact the truck runs great. Accelleration is great, milage is where its supposed to be.



I dont know if its related, but I did the rewire (i think they called it the southbend rewire or something) and put on the noise ground filter from diesel technology (i think) because of the TC lock/unlock problem... which I havent had since I did those two things.



Mine is a 99... Would the DRBIII be able to turn on & off injectors to see if that was the problem on mine too or is that for other problems?

Craig

 

[JLandry]

Mine is a 99... Would the DRBIII be able to turn on & off injectors to see if that was the problem on mine too or is that for other problems?

Craig,



Yes. Either a Chrysler DRBIII scan tool or Cummins Insite software (with appropriate cables and connectors) can selectively kill injectors on a 98. 5 and newer truck. I think this feature is primarily intended to help a mechanic quickly isolate an injector which is suspected of malfunctioning. For example, if your engine were running rough constantly, you would kill one injector at a time listening for change in engine sound and rpm. If the engine sounded worse when killing a particular injector, then you could safely assume you just killed an injector which was functioning properly. If there was no change in sound or rpm, then you could assume the injector wasn't working.



An alternative to using a DRBIII for this kind of test is to simply loosen the high pressure injection lines one-at-a-time at the cylinder head with the engine idling. When a line is loosened the respective injector will stop firing.



But in your case with the engine only running rough intermittently, killing injectors would likely be inconclusive.



John L.

 

[ALepley]

Craig,



Yes. Either a Chrysler DRBIII scan tool or Cummins Insite software (with appropriate cables and connectors) can selectively kill injectors on a 98. 5 and newer truck. I think this feature is primarily intended to help a mechanic quickly isolate an injector which is suspected of malfunctioning. For example, if your engine were running rough constantly, you would kill one injector at a time listening for change in engine sound and rpm. If the engine sounded worse when killing a particular injector, then you could safely assume you just killed an injector which was functioning properly. If there was no change in sound or rpm, then you could assume the injector wasn't working.



An alternative to using a DRBIII for this kind of test is to simply loosen the high pressure injection lines one-at-a-time at the cylinder head with the engine idling. When a line is loosened the respective injector will stop firing.



But in your case with the engine only running rough intermittently, killing injectors would likely be inconclusive.



John L.

A snap-on solus pro or modis is capable of injector cut outs well. Thought I'd run that by.

 

[JLandry]

A snap-on solus pro or modis is capable of injector cut outs well. Thought I'd run that by.

Good to know!



Thanks,



John L.

 

[Ncostello]

My 99 did this same thing. Turn on the AC which puts a little load on it. That made mine go away slightly. Mine would only do it with no load idle. A new lift pump and my RV275 injectors didn't cure my problems either. And Scheid scanned the truck with Insight... saying that it couldn't be narrowed down to one injector or the other. Because they were missing randomly. All of them... here and there. So shutting off one at a time just meant the other 5 had a chance to miss just the same. Or not. In short... it sounded like one bad injector, but all 6 were missing and from no fault of the injector. It's really annoying isn't it?



BlueChip Diesel says:



"Rough idle/miss at light throttle is almost always the computer on the top of the injection pump, as long as there is appropriate lift pump pressure, no air in the fuel lines and no codes pertaining to Crankshaft or Camshaft sensors. By now you know what a bad computer means; REPLACE THE VP44!"

 

[firefighter_2000]

Thats what Im thinkin

Thats kinda what Im thinkin... Hate to drop a lotta money on a blue chip... . But dang, I know they're probably the best. Tax time is coming!!!

Craig

 

[DCreed]

be sure non of the injection lines are cracked or leakage at the tubes as it causes the same issue.

 

[firefighter_2000]

Check

Checked those... They're all good. Im thinkin I may need a new pump. I REALLY would like to go with a blue chip, but crap :{ thats a lotta cash. I guess I could just go ahead and drop the 2500 for a blue chip pump and a new FASS pump. #@$%!

Craig

 

[DCreed]

If you're gonna spend that much, swap to a Ppump and never worry again.

 

[firefighter_2000]

I dont think...

I dont think I'd be able to do that myself... Who does that modification, and how much does it cost?

Craig

 

[AlaskanCummins]

I thought about doing the P-pump before I purchased Chips X pump. The cheapest way I found would be to get a real high mileage or blown 12v because the parts are about 1500-2000 EXCLUDING the pump itself. I figured I'd have about 4K in a P-pump conversion.



So I opted to just get a 2K dollar Blue Chip pump and I'm EXTREAMLY happy with it so far. If you're going to purchase a new VP, I'd say go with Chip and no one else.