philbar715
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(Im copy/pasting this from the hptuners forum so ive got hptuners log files attached, the video, and the hptuners tune file attached.
Log of noise at idle - https://drive.google.com/file/d/1WpY...usp=drive_link
Log of noise while coasting - https://drive.google.com/file/d/15T0...usp=drive_link
I purchased a 2015 GMC Yukon (l83 5.3 and 6l80) in September with 215k miles. Around 175k miles the transmission was replaced with a rebuilt unit and a billet "HD" torque converter. Supposedly around 190k miles the cam and lifters were replaced with GM parts and AFM system intact.
In October after I put about 500 miles on it after buying it the engine developed a severe lifter tick. I started the teardown process and found a few trashed lifters and chewed up cam. I began the work to replace the cam/lifters with non DOD components when the timing chain tensioner snapped. I then pulled the engine. With the engine out, I inspected and found some scoring on the crankshaft bearing surfaces and decided to replace it with a rebuilt shortblock and rebuilt heads.
Original vac pump deleted, and brake booster is getting vac from a tee off of the intake manifold along with a catch can. Nothing unusual in the catch can other than some condensation due to where I have it mounted and a couple of drops of clean oil.
I purchased a stock rebuilt L83 longblock (casting matched original engine), L8T cam, delphi LS7 lifters, and associated timing parts, gaskets, etc. I put it all back together over the period of a month.
Last week I was able to fire it up for the first time on the new parts. The engine ran very well (after lifters pumped up, they were noisy for about 2min on first startup) and I put about 10 miles of mild driving on it where I kept it in tow haul mode to get some engine braking to seat the piston rings. On accelerations I used a max of 75% throttle and 4500rpms about three times.
After that test drive I was going to change the differential fluids and as I drove it in the garage I heard some weird knocking noise (not knocking like rod/lifter) this is almost like a "puff" that was reverberating through the intake manifold and out of the air intake tube. It is exactly inline with valvetrain RPM and to me it sounds like one valve is doing something it is not supposed to.
I've attached a video because there is no way for me to describe this sound. https://photos.google.com/photo/AF1Q...MJgjroxNYYJlRl
I was also able to log it while it makes this noise and you can clearly see it in the MAF readings as well as a little bit in the MAP readings. it happens about once every second. In this screenshot where the MAF/MAP went flat it stopped making this noise all on its own while I wasnt touching it. A few other times during this log I was double checking vacuum lines/breather lines/etc and pulling some of them off so you'll see the fuel trims go crazy thats just me messing with some stuff. I also did disconnect EVAP to rule that out.
This is where it gets weird, I took the valve covers off and verified there are no broken springs or rocker arms that were not torqued correctly. I did not remove rocker arms or pushrods but from what I could tell there were no broken/bent pushrods. I removed the intake manifold and found nothing in the intake valves, two intake manifold gasket runners were slightly squished and out of place that could have been causing a tiny vacuum leak. I fixed those and verified the manifold went back on with no issues and all gaskets in place.
The next time I started it up it did not make the noise, ran quiet and smooth for about 1 min then it started making the same noise again. Then it would randomly stop anywhere from 5 seconds to a whole min before it would do it again. Then eventually it stopped making this noise all together and would idle smooth and quiet like it should.
Now this issue only appears sometimes when the engine is warm but not fully warmed up and while coasting down the road with no throttle. You cant hear it from inside the cab, you can only see it in the logs in the MAF/MAP readings. under acceleration and normal cruise it does not appear to have any issue. So far ive driven about 200 miles on this rebuilt engine with no other major issues that I know of, power seems good and MPGs seem good as well.
Im looking for a few ideas/help/troubleshooting. I've attached the current calibration and log files where I was able to capture it.
Full parts list
GM L8T cam - 12672469
Delphi Ls7 Lifters
GM timing chain tensioner
New GM timing gear cam phaser
new plastic lifter trays
plenty of assembly lube on everything
Rebuilt heads, mating surface machined
New GM injectors, fuel rails, fuel rail pressure sensor
new spark plug wires
2 new spark plugs, 6 have about 200 miles on them from when i replaced them before the rebuild
L86 Intake manifold
L86 throttle body
AFE intake
original coilpacks
Log of noise at idle - https://drive.google.com/file/d/1WpY...usp=drive_link
Log of noise while coasting - https://drive.google.com/file/d/15T0...usp=drive_link
I purchased a 2015 GMC Yukon (l83 5.3 and 6l80) in September with 215k miles. Around 175k miles the transmission was replaced with a rebuilt unit and a billet "HD" torque converter. Supposedly around 190k miles the cam and lifters were replaced with GM parts and AFM system intact.
In October after I put about 500 miles on it after buying it the engine developed a severe lifter tick. I started the teardown process and found a few trashed lifters and chewed up cam. I began the work to replace the cam/lifters with non DOD components when the timing chain tensioner snapped. I then pulled the engine. With the engine out, I inspected and found some scoring on the crankshaft bearing surfaces and decided to replace it with a rebuilt shortblock and rebuilt heads.
Original vac pump deleted, and brake booster is getting vac from a tee off of the intake manifold along with a catch can. Nothing unusual in the catch can other than some condensation due to where I have it mounted and a couple of drops of clean oil.
I purchased a stock rebuilt L83 longblock (casting matched original engine), L8T cam, delphi LS7 lifters, and associated timing parts, gaskets, etc. I put it all back together over the period of a month.
Last week I was able to fire it up for the first time on the new parts. The engine ran very well (after lifters pumped up, they were noisy for about 2min on first startup) and I put about 10 miles of mild driving on it where I kept it in tow haul mode to get some engine braking to seat the piston rings. On accelerations I used a max of 75% throttle and 4500rpms about three times.
After that test drive I was going to change the differential fluids and as I drove it in the garage I heard some weird knocking noise (not knocking like rod/lifter) this is almost like a "puff" that was reverberating through the intake manifold and out of the air intake tube. It is exactly inline with valvetrain RPM and to me it sounds like one valve is doing something it is not supposed to.
I've attached a video because there is no way for me to describe this sound. https://photos.google.com/photo/AF1Q...MJgjroxNYYJlRl
I was also able to log it while it makes this noise and you can clearly see it in the MAF readings as well as a little bit in the MAP readings. it happens about once every second. In this screenshot where the MAF/MAP went flat it stopped making this noise all on its own while I wasnt touching it. A few other times during this log I was double checking vacuum lines/breather lines/etc and pulling some of them off so you'll see the fuel trims go crazy thats just me messing with some stuff. I also did disconnect EVAP to rule that out.
This is where it gets weird, I took the valve covers off and verified there are no broken springs or rocker arms that were not torqued correctly. I did not remove rocker arms or pushrods but from what I could tell there were no broken/bent pushrods. I removed the intake manifold and found nothing in the intake valves, two intake manifold gasket runners were slightly squished and out of place that could have been causing a tiny vacuum leak. I fixed those and verified the manifold went back on with no issues and all gaskets in place.
The next time I started it up it did not make the noise, ran quiet and smooth for about 1 min then it started making the same noise again. Then it would randomly stop anywhere from 5 seconds to a whole min before it would do it again. Then eventually it stopped making this noise all together and would idle smooth and quiet like it should.
Now this issue only appears sometimes when the engine is warm but not fully warmed up and while coasting down the road with no throttle. You cant hear it from inside the cab, you can only see it in the logs in the MAF/MAP readings. under acceleration and normal cruise it does not appear to have any issue. So far ive driven about 200 miles on this rebuilt engine with no other major issues that I know of, power seems good and MPGs seem good as well.
Im looking for a few ideas/help/troubleshooting. I've attached the current calibration and log files where I was able to capture it.
Full parts list
GM L8T cam - 12672469
Delphi Ls7 Lifters
GM timing chain tensioner
New GM timing gear cam phaser
new plastic lifter trays
plenty of assembly lube on everything
Rebuilt heads, mating surface machined
New GM injectors, fuel rails, fuel rail pressure sensor
new spark plug wires
2 new spark plugs, 6 have about 200 miles on them from when i replaced them before the rebuild
L86 Intake manifold
L86 throttle body
AFE intake
original coilpacks
