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Hello all- Cm871 bad vibration while using engine brake on high position when turbo boost reaches about 23-24 psi boost and above. Oddly it occurs only about 75 percent of the time.

It also has same vibration between 1500 and 1600 rpm on the go pedal on the way up through the range.

All sensors are new and both jake rocker shafts were changed six months ago which seemed to improve things a bit but is still mostly the same. I had a jobber rebuilt actuator on for 4-5 months and switched to an oem rebuilt actuator but that didn't fix the problem.
Tune is RRough

I'm suspecting turbo which is {non oem} reman on there about two years and can't remember if it was vibrating on old one or what the reason was for changing it then.


Another thing it does is when we go down hills on high position it will boost up to 30 psi but fluctuate up and down to lower 20's when its not vibrating {why I switched actuator}

Has around 10k hrs at moment and overhead done multiple times over last 2 years.
Anyways thanks; any help is appreciated

I had one that did that and it was a bad injector. I ran an injector test and it came up as 1 of the injectors failed one of the test. The truck ran good but as soon as I replaced the injector the vibration went away when the Jake’s were one.

could be bad/leaky injector(s).. do an injector leak test on it.
ref: http://rawze.com/forums/showthread.php?t...8#pid67948

Also could be leaky fueling actuator(s) too.

I think I have a leaky injector I ordered the test tool
Thanks

I usually let prime pump cycle fully in the morning as it seems to not keep fuel pressure. Overnight the reading on fuel pressure is -1 psi then immediately up to around 250 psi on startup then -1 after shutoff
Never blows smoke on startup but sometimes blue smoke puff when coming off jake at low rpm and slow speed

My Prostar would shake on stage 3 engine brake. It turned out to be the connector for the engine brake solenoid on cylinders 4-5-6. I used pliers to tighten the spade connector and put it back on. That solved my vibration on stage 3.