2014 isx vibration

[race7820000]

ok, so I bought a 2014 579 pete a month ago with a isx motor.10spd

when I test drove it I noticed it had a very slight vibration when accelerating and I assumed it was because I was bobtailing and truck was sitting for a few months.

when you hook up to a trailer (empty) the vibration gets worse. when the trailer is loaded and you apply a lot of torque like going up a hill the dash will vibrate almost like a washboard. (1250-1350rpm) but when it doesthat and you let up on throttle even a little bit then it goes away.

The vibration is worse when motor is under a load, but if you let off the throttle it goes away. it only does it when your accelerating.

I have taken it to peterbilt,kenworth and cummins

I have had the ride height, u joints,rear end, carrier bearing etc etc checked 3 times.All good

had truck aligned also and installed new tires , virgins , thinking it would help...it did not

Cummins put the truck on a dyno and recreated the vibration

They did all the engine performance tests with the fuel inject,pressure etc etc. all of them passed

They said motor sounds goofy like its detonating, they changed accuator and accuator housing because they thought it was dumping to much fuel.

Finnally they gave up and said they think vibration is in motor but they don't know what it is without tearing it apart.

today I noticed the davco fuel filter looked like it needed changed because it was full, but when they did the dyno test a cpl days ago the fuel level was at the bottom, I changed it anyways and no difference.



I am hoping someone else has had this problem because im about ready to light a match and walk away....slowly lol

thanks

[Rig Wrench]

Sounds like possible pilot bearing failure

[Isx Lover]

When was the overhead set last?

[race7820000]

the overhead has never been done, has 430000 miles on it, but cummins said the overhead wouldn't cause the vibration/shaking problems.

[Unilevers]

honestly, what you are describing is too low of a final crank angle. This happens alot when tuning them and the timing is too far advanced for the amount of fuel your running. Now its more rare in stock cals, BUT ive seen trucks that overfuel from stock (drippy injectors, fuel pump actuator, wrong cal in the truck, etc) that do this. It's caused by the pistons hammering the crank less than 4 ATDC and you just hammer your rods into your crank and you get the famous big boy "Power vibration". on a stock truck you will not see if it is actually overfueling due to all the emmisions equipment.

this is easy to test. flash the lowest hp file for your CPL and test it again - my bet is is mostly goes away. another option is to have someone manually retard the timing about 2 degree's and try again. My bets are it doesnt come back when this is done.

many many people i talk to tell me they have been chasing this mysterious vibration for months and cannot find it. they think its driveline, rear ends, tranny, etc - but really its the engine destroying itself from the inside. rod bearings do not last very long with this condition. i just back the timing off a few degrees and its gone - but in a stock truck you will need to find the cause of this overfueling.

[Rawze]

(03-05-2016 )race7820000 Wrote:  the overhead has never been done, has 430000 miles on it, but cummins said the overhead wouldn't cause the vibration/shaking problems.

It sounds like your dealing with the typical under-trained idiot squad (not that I am less of an idiot myself lol).

I have seen ISX vibrate for all the reasons that they looked for. dirveline, clutch, damper, etc.

But they will also vibrate like that if ...

* there is a spun bearing in the head and it is now wallowed out.

* Bad Overhead adjustment. - An overhead need to be done on ISX every 200k miles or so, not 400k+, like the book says. That is a good way to loose your cam prematurely ( more info on overhead cams )


* bad fuel-to-air ratio (on a CM2350 that would be more than 32-33 lbs boost in most cases).

* bad ecm programming.

* injector problems.

* static timing problems.

* excess exhaust back-pressure from a clogged emissions system.

* an over-spooling turbo.

* A bent rod or wrist pin problem

* engine cavitation due to charge flow restrictions.

* worn out main or rod bearings, or overhead cam bearings.

-- that is just what comes to mind off the top of my head.

[race7820000]

Well I was courious and went to cummins today, they did the overhead and said there was a couple exhaust that were a little tight but still within speck.

Still runs the same

[race7820000]

Also They did update the ecm, they said it was on a super old update and hasent been done in awhile

[race7820000]

How do you set the timing?