Low RPM stutter

[Eric_77]

I seem to be having a problem with my 96 truck just showed up in last 500 miles or so (last tank) at idle in gear the truck throws a shake through whole truck real bad seems to be about every other revolution; every time one cylinder fires. Stutter seems to be there even in neutral but whole truck doesn't get the shake.
How can I isloate which cylinder it is or does it even matter? Is there an injector cleaner for diesels? my injectors are still stock time to replace? If so I remember hearing a while back about some new smokeless high-pro injectors who has them how much?

Fuel economy seems normal 550 miles on 27 gallons and pulled trailer yesterday mostly loaded and it did fine but seemed to stall more than normal; normal being stop and go traffic if I back off gas real fast from <1200 RPM in first the low stall converter kills motor.

It seemed to have similar problem last winter but it went away as truck warmed up this is not.

I am burning about 1/4 quart every 5k miles so I think motor is still in good shape. Time for oil sample test? If I do a test who should I send it to? Does one test do any good or do you need several tests to do a comparision?

Sorry for all the questions but my mechanic moved and now am looking for new one. Any ideas on good Cummins mechanics in Dallas area? The Dodge house (Auto Nation Dodge) said they do not have a diesel certifed mechanic in house now and said to go to Cummins. Good? Bad?

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Eric Kelcher
92 W250 stock 4spd/auto 3. 54
96 2500 extd SLT Diesel Dynanics fuel pump plate; auto with DD shift kit(?) Dun-Rite TC; 3. 54 posi; K&N airfliter; Boost, transmission temp, EGT guages waiting for nice day; 192K
13. 5k 33'utility trailer 19' Galaxie runabout

 

[Andy Redmond]

I can help, email off list and I'll get your my phone numbers.

I have several suggestions for your complaints.

However, I recommend some Cummins injector cleaner or other quality injector cleaner.

You can see it you have an injector problem, by letting the truck idle and carefully loosening each fuel line slightly at the injector. Wear safety glasses and skin protection. You have HIGH psi diesel that can easily poison one, if it's injected into ones skin! #ad


My other thoughts are fuel psi, restrictions, sticky delivery valves, pump plungers, dirty injector(s) malfunctioning governor. etc. .

Good luck
Andy

 

[Missouri Mule]

Eric_77,

How does the engine run when in neutral or park?
Do you get the violent shake when in park/neutral?
"Idle in gear" is that at stand still or rolling?
Could be engine problems if problem is also occuring in neutral or park.
But sounds like trans problem to me depending on the answers to the questions.



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Bill Thomas
Missouri Mule - 96 Wht 4X4 ST CC,5 spd, 3. 54, 8 ft bed, 1 ft high cheater boards.
99 Freightliner bl/wht FL60 ISB-5. 9 24v,215 hp,520 tq,6 spd, 3. 59 nsr,16 ft box, 19. 5 tires,Wt/gvw 11,000/23000

 

[Missouri Mule]

Mite of jumped timing(or out of it. ) for some reason, this could cause vibrations. Main bearings(usually low oil pressure),rod bearings also vibration.
Leading and simple cause is universal joints.

Of course auto trans could be causing it.

 

[illflem]

It sounds like you may have an injector pump plunger that is sticking. Your idea of fuel additive is a good one, use a double dose. You can isolate which injector/plunger is causing the problem by cracking open the fuel line at the top of each injector one at a time while the engine is running with it's problem. As you crack the lines open the engine will run worse till you get to the faulty one then it will make little difference. Don't know how much good it will do you though, you may need the pump rebuilt or injector replaced, best find an expert.

 

[Eric_77]

Shake is always there just not whole truck shake like when in gear with foot off brake. Stop and go traffic idle, shake is worst. I am going to get injectors cleaned then see what happens.

transmission I think is weak but I don't want to spend 1700 on new transmission when motor might be having problems. I don't know how to describe it but it doesn't seem "right" to me anymore but it could be fine.

 

[Eric_77]

Wouldn't timing cause a more severe stumble and shake off idle? Motor runs perfect off idle no shake.
I will check out those U-joints, as they have never been replaced, but the fuel additive seems to be working I may try another just to be sure and get it real clean. The shake is almost totally gone but still a wiggle from motor every few revs.

 

[Missouri Mule]

Eric,
If your dramatic shake has stopped it was probably a clogged injector of dirty injector pump.
I was listing things I know could cause vibrations(shaking). I was thinking injector pump could be off little and needed to be timed if it hasn't been done for a while. But did short version, if it had jumped time would of been running bad most of time and hard to start. My experience with two engines was that I felt a vibration(at low rpm) several hundred miles before the main/rod bearing went. The univeral joints usually vibrate at low speeds. On a ford van I had the center carriage bearing caused low speed vibrations also. But you were not moving when things were acting up.
But I was talking to a guy that runs sod trucks and he said probably dirty injector. Would cause problems at low rpms because not enough pressure to get fuel thru dirt but at high rpms/speeds it would have more pressure and engine would run about normal.
I thought trans could be causing stalling.
How is stalling problem has it gone a way also?

[This message has been edited by Missouri Mule (edited 05-23-2001). ]

 

[Joe G.]

Eric,

This may be a dumb question, but what RPM is it idling at? If these things are a little low on idle speed they can bash around pretty good.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,DTT TC/VB,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver, KDP 160,000-NM-WT Insurance