Rough idle, no smoke, runs fune but vibration at higher speed

[Maz1885]

I have a bone stock 2005 dodge ram heavy duty quad cab 2500 5.9, 4x4 AT long wheelbase with 211k + miles. Engine had been running rough at idle in park and neutral and if i bring the rpms up slowly or whack the pedal the roms are slow to come down kinda bouncing and hanging ubtil it returns to idle. It drives fine once going until i stop at a light or sign then runs rough again. I did have a problem with the rpms hanging while driving, like cruise was on after letting off pedal but changing the fuel rail pressure relief valve seemed to calm that down to almost non existent. Changed crank sensor, intank lift pump, fca, fuel rail pressure relief valve, fuel rail pressure sensor and had a complete overhaul of the original ipm done. Fuel rail pressure seems to be good between 5-6000 at idle and steadily climbs up the scale. Got to about 18000 at around 2500 rpms but never went wot. Did an injector return flow test and got 150ml for one minute at idle with engine warmed up. Checked all wiring no chaffing. All grounds and battery cables clean and good connections. Injector solenoids ohmed within limits from what I've been reading, less than 1, so could this be that the injectors are just worn out? I'm at a loss here.

 

[cerberusiam]

Likely injectors at that mileage. 2005 injectors had none of the updates that the latest revision has. Another quick test is in neutral or park, run rpms up to 3000, hold for 15-20 seconds, then lift all the way off the throttle. If the rpms step down with little hangs instead of smoothly drop to idle it is injectors. Return flow just tells you whether the internals are worn on the bypass circuit, nothing about operation. You need to do a cylinder contribution test and rpm drop on injector kill to get a better idea of the injector health. The return flow at idle is not a good indication, has been superseded with a better test.

If you do not run an additive package that would be where I would start. Drain the fuel filter housing and fill it with your favorite injector cleaner, start and run engine for about 30 seconds then shut it off and let sit for 24 hours. When you start driving it again dose the fuel with a quart of Power Service, a quart of 2SO, and a quart of MMO in a full tank of fuel. After that mix 96 ozs of Power Service with a quart of 2SO and add 10-12 ozs of mix per 1/2 tank of fuel when you fill. Might just be gummed up and you can get some more miles with additive usage.

The real test is fuel mileage, if that stays significantly lower the injectors are wounded.

 

[Maz1885]

Yes rpms come down with hanging in between. I have been using power service regularly for many years. Did the fuel filter change and dosing of diesel kleen, No change. Gonna run a test on the injector pump. If it's good i guess I'll start pulling injectors.

 

[Ozymandias]

Injectors like Cerb says, old and worn. To bad you wasted so much money for all the surroundings.
And for Injectors, do yourself a favor and buy BBi, remanufactured or New.
There is to much crap for sale out there, some even claim new but selling almost 20 year old stocks.