got cm871 uni tune m*m**2 engine started rattling, sound's like valves or rocker's. did top end yesterday minus injectors ,don't have dial torque wrench . everything looked ok. barely any adjustment needed, 1/4 turn on set screw at most, all jake rockers steady when idling. noise starts once i hit 30 lbs of boost climbing, dropped rpms to under 15 and would almost stop the noise but lugging engine, last hour had to keep boost under 30 psi noisy pulling down to 1300 rpm. thinking might be loosing an injector. dont know what else going to plug in and try cylinder cut out test but more likely be going to dealer today , can't drive like this afraid something going to break.
get the right wrench and adjust the injectors too.
then do an injector leak test.
how old is the engine? - miles, some hsitory? etc/.
Interesting. Could be one of the injectors is over fueling when it sees boost. DO bubble test and see if you have a bad injector... But to me a over fueling injector would have more of a knock sound than a rattle though.
What kind of truck you driving? Just thought about one we had was a 379 peterbilt when you started pulling it would rattle end up the clutch was tight and had a harmonics coming from driveline under load up through the clutch linkage. We greased and adjust clutch linkage noise went away.
As far as valve rattle I may be wrong but I dont think those will matter under boost or not.
Also had one that had a random rattle under valve cover and the jake rocker was the issue where the detent on the rocker shaft was worn very bad and it would allow the jake rocker sit there and slap the camshaft every now and then...
This is just a few issues I have seen. If you find what it is please let us know this is very interesting.
app 200 thousand miles on long block rebuild 2 years ago . built in mexico its an LB8 motor had uni reprogram for lessor power to drop boost below 40psi was hitting 43 on old engine oil always done around 10,000 miles changed rocker shafts on intake side in summer cause jakes where rocking at idle, then did top set about month latter and thought valves where sinking into head because clearance on jakes from detent where low turned out was my mistake switching from feeler gauges ( set them to .251 instead of .276 . could an injector make a rattle noise? the higher the rpm the louder the noise.
when i did rocker shafts i changed spring and plungers as well on idle the do not move at all but if rockers themselves are worn internally on bearing could they start moving at higher rpm's
Mr Hagg how long a wait to get into your shop i'm about 2 day drive down if i can't get this done on my own or shop up here is no good i will probably come down to see you
Call in 678-688-8107 they will get you on the board. Its crazy theses days some weeks we are book and noone shows and some weeks we are half booked and end up being slammed all week.
Update so it turned out to be the clutch release bearing just like Mr Hagg suggested I check. thank you so much for that advice. I never would have believed it would sound just like valve's rattling. I pulled the remote grease line and put a grease fitting directly to bearing took 27 pumps for grease to come out noise completely gone.
Thank you for letting us all know. This is why I love forums like this we all can play part of making things easier.