Help me solve this problem.....
Help me solve this problem..... Ok so i built a turbo 5.3 boosted it for a while at 12psi, broke a ringland due to ring gap way to tight...
threw a new (good used) piston in, arp rod bolts, new head gaskets, arp head bolts, meth injection, ect....
I drove it and boosted 12psi for a while and it was great no problems...
I had the main power wire short out (relocated to back and wire rubbed)... but pcm seems to be working fine, but not sure what else to blame it on.
THE PROBLEM: it has an issue building boost past 3-5psi! It will studder hard and just not accelerate! There are no nocks, ticks, abnormal sounds, or KR in logs except for at idle and LIGHT throttle...
AFR is good and IATs are in the 60* area
tried to richen a little and lean out a little
tried lowering and adding timing, its not burst kr since im getting all timing commanded
tried turning meth injection off
NO KR showing on logs
Cant find an intake leak (tested via propane and carb cleaner) --- not 100% sure its ok though
tr6 plugs look great and gapped at .28
plug wires look good
all coils are working
all injectors are working
cylinder balance test shows 99% and 98% on all cylinders
grounds look good but i may try loosening and retightening them
motor has quite a bit of blow-by but that is due to larger ring gaps....
Im not sure what else to look for on this thing! Its like i hit a brick wall and it just sputters like crazy and wont accelerate any more, this is only when i get into a little boost, non boosted areas it doesnt do it.
Any ideas? Thanks!
threw a new (good used) piston in, arp rod bolts, new head gaskets, arp head bolts, meth injection, ect....
I drove it and boosted 12psi for a while and it was great no problems...
I had the main power wire short out (relocated to back and wire rubbed)... but pcm seems to be working fine, but not sure what else to blame it on.
THE PROBLEM: it has an issue building boost past 3-5psi! It will studder hard and just not accelerate! There are no nocks, ticks, abnormal sounds, or KR in logs except for at idle and LIGHT throttle...
AFR is good and IATs are in the 60* area
tried to richen a little and lean out a little
tried lowering and adding timing, its not burst kr since im getting all timing commanded
tried turning meth injection off
NO KR showing on logs
Cant find an intake leak (tested via propane and carb cleaner) --- not 100% sure its ok though
tr6 plugs look great and gapped at .28
plug wires look good
all coils are working
all injectors are working
cylinder balance test shows 99% and 98% on all cylinders
grounds look good but i may try loosening and retightening them
motor has quite a bit of blow-by but that is due to larger ring gaps....
Im not sure what else to look for on this thing! Its like i hit a brick wall and it just sputters like crazy and wont accelerate any more, this is only when i get into a little boost, non boosted areas it doesnt do it.
Any ideas? Thanks!
I chased my dang tail for weeks in the tune trying to figure out something similar. It turned out that a coil was only partially charging. I forget the particulars, but when scoped I think the others showed 40k volts and that cylinder was only hitting 20k. Any heavy load and it would misfire and studder and refuse to make boost. What are your air fuels doing when it stops making boost?
Do a compression and leak down first thing. Was the first 5.3l pulled apart and the gaps set too tight? If it was a stock engine with stock rings the tune up killed it not the ring gap.
Put a fresh set of plugs in it or bead blast them, make a pull and shut it down and pull them. You might be able to pin point the cylinder(s) with the problem at least. This is almost impossible to do on old plugs.
Put a fresh set of plugs in it or bead blast them, make a pull and shut it down and pull them. You might be able to pin point the cylinder(s) with the problem at least. This is almost impossible to do on old plugs.
Ok thanks for the tips guys! I will try the coils (i have a few sets around so itll be free if thats the issue) and compression test (also free hahahaha)... if i dont find anything ill buy a new set of pulgs and check them after a run..
If anyone else comes up with an idea im open ears....... im going out to the shop to check that stuff now... ill report back with results!
If anyone else comes up with an idea im open ears....... im going out to the shop to check that stuff now... ill report back with results!
The cylinder compression was done on a cold motor...
cylinders checked in this order:
#7 - 140 (assuming lower because of older used 5.3 piston and slightly larger ring gap)
#5 - 150
#3 - 150
#1 - 170
#8 - 155
#6 - 160
#4 - 155
#2 - 155
Nothing looks horrible enough to cause the issue im having....
cylinders checked in this order:
#7 - 140 (assuming lower because of older used 5.3 piston and slightly larger ring gap)
#5 - 150
#3 - 150
#1 - 170
#8 - 155
#6 - 160
#4 - 155
#2 - 155
Nothing looks horrible enough to cause the issue im having....
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
No major ramp rates in fueling, PE starts lower and ramps up, so does boost enrichment....
I tried leaning and richening up in that area with no luck... also played with timing...
...........................
been working on my dads 47 Ford ls swap all night havent had time to mess with my c10 much, ill check the turbo quick tho! Ill update in a few with what i find.
THANKS EVERYONE FOR THE HELP!
Turbo and wastegate are working fine.....
Thinking my wideband 02 might be messed up... i went to recalibrate it (NGK Powerdex) and it wont go to cal- it just stays at 16.00 and its been in open air for 3 hours lol....
Have a new NTK O2 on the way... this might be the issue i might be way rich..
I am down to injectors, plugs, intake, valvespring, pushrod, PCM, MAP sensor, bad wires....
This is really throwing me off, probably just a simple thing im overlooking HAHAHAHAHA
Thinking my wideband 02 might be messed up... i went to recalibrate it (NGK Powerdex) and it wont go to cal- it just stays at 16.00 and its been in open air for 3 hours lol....
Have a new NTK O2 on the way... this might be the issue i might be way rich..
I am down to injectors, plugs, intake, valvespring, pushrod, PCM, MAP sensor, bad wires....
This is really throwing me off, probably just a simple thing im overlooking HAHAHAHAHA
TECH Fanatic
Joined: Oct 2011
Posts: 1,425
Likes: 0
I hate to say this but when my motor went, I threw in a complete new engine and it did the exact same thing as yours. It would rev just fine but if I put it under load I could not for the life of me get it to build past 5lbs of boost nor go past 3500 rpms. Tried changing cams, plugs, wires, pcm, etc..
It was the damn turbo. Bought a new turbo and put it on, problem fixed. I will bet that when the engine went some metal got in the oil and ate up the turbo bearings. Mine looked and sounded like it was working. When I sent it in they said it was shot.
It was the damn turbo. Bought a new turbo and put it on, problem fixed. I will bet that when the engine went some metal got in the oil and ate up the turbo bearings. Mine looked and sounded like it was working. When I sent it in they said it was shot.
I hate to say this but when my motor went, I threw in a complete new engine and it did the exact same thing as yours. It would rev just fine but if I put it under load I could not for the life of me get it to build past 5lbs of boost nor go past 3500 rpms. Tried changing cams, plugs, wires, pcm, etc..
It was the damn turbo. Bought a new turbo and put it on, problem fixed. I will bet that when the engine went some metal got in the oil and ate up the turbo bearings. Mine looked and sounded like it was working. When I sent it in they said it was shot.
It was the damn turbo. Bought a new turbo and put it on, problem fixed. I will bet that when the engine went some metal got in the oil and ate up the turbo bearings. Mine looked and sounded like it was working. When I sent it in they said it was shot.
The turbo will free wheel for a LONG time after key is turned off, end play feels ok on both sides...... guess its possible it could be the problem though
TECH Fanatic
Joined: Oct 2011
Posts: 1,425
Likes: 0
Yeah, mine looked like it was working fine. I would have never guessed it was the turbo. I now have junk chinese turbos on it and it runs 25lbs of boost when I want to and bounces off the rev limiter. Problem solved.
Once you find out let us know.
Once you find out let us know.
