turbo 5.3 pulling and missing??
turbo 5.3 pulling and missing?? Alright guys got my car on the track for the second time now, I noticed the car falls on its face above 6200 along with a nasty backfire...currently running 16lbs not sure what h.p is but it did 640 wheel on 10 #'s ?? Car did pretty good a 6.8 @ 110 in the 1/8th through a 6 speed breaking loose in 2nd ..question is what would cause the missing up top...back pressure, valve springs,fuel press?????? Not sure where to start looking..has new wires and plugs..any input is greatly appreciated..
No logging and I don't have a wideband yet ,im gonna pick up a fuel press gauge today so I can monitor ..
..cam "tu1.5" 228/228 571/571 112 LSA lunati dual gold springs good for 650 lift I believe..
Bp7efs gapped at 24 I would get blowout underload at anything higher ..
Fuel : magnafuel 4303 -10 feed -8 return
Aeromotive 1:1 fpr
Fic 1000cc injectors
E85..
Turbo: turbonetics 7875 .96 3" Down pipe dumped ..
My springs had some miles on them before being boosted around 25k ..
Can it be possible that there getting weaker?? Possibly losing pressure??
Maybe bring spark plug gap down a little more?
..cam "tu1.5" 228/228 571/571 112 LSA lunati dual gold springs good for 650 lift I believe..
Bp7efs gapped at 24 I would get blowout underload at anything higher ..
Fuel : magnafuel 4303 -10 feed -8 return
Aeromotive 1:1 fpr
Fic 1000cc injectors
E85..
Turbo: turbonetics 7875 .96 3" Down pipe dumped ..
My springs had some miles on them before being boosted around 25k ..
Can it be possible that there getting weaker?? Possibly losing pressure??
Maybe bring spark plug gap down a little more?
TECH Resident
Joined: Sep 2013
Posts: 993
Likes: 119
From: Mechanicsburg, PA
With no data it's hard to speculate. But with that said, it's easy enough to tighten the gap and run it again. It also could be a lean misfire as well. So be careful leaning on it too much until you have a wideband and can safely see what it's doing. A valve spring getting weak is always a possibility as well. It also could be a coil getting weak as well, although not common. You can check output with a simple/cheap ST125 type tester.
Good luck!
Lon
Good luck!
Lon
Trending Topics
TECH Enthusiast
Joined: Mar 2010
Posts: 519
Likes: 2
No logging and I don't have a wideband yet ,im gonna pick up a fuel press gauge today so I can monitor ..
..cam "tu1.5" 228/228 571/571 112 LSA lunati dual gold springs good for 650 lift I believe..
Bp7efs gapped at 24 I would get blowout underload at anything higher ..
Fuel : magnafuel 4303 -10 feed -8 return
Aeromotive 1:1 fpr
Fic 1000cc injectors
E85..
Turbo: turbonetics 7875 .96 3" Down pipe dumped ..
My springs had some miles on them before being boosted around 25k ..
Can it be possible that there getting weaker?? Possibly losing pressure??
Maybe bring spark plug gap down a little more?
..cam "tu1.5" 228/228 571/571 112 LSA lunati dual gold springs good for 650 lift I believe..
Bp7efs gapped at 24 I would get blowout underload at anything higher ..
Fuel : magnafuel 4303 -10 feed -8 return
Aeromotive 1:1 fpr
Fic 1000cc injectors
E85..
Turbo: turbonetics 7875 .96 3" Down pipe dumped ..
My springs had some miles on them before being boosted around 25k ..
Can it be possible that there getting weaker?? Possibly losing pressure??
Maybe bring spark plug gap down a little more?
Swapped plugs for fresh ones, swapped them out for some tr6s as well after that. Did plug wires, changed to truck coil packs too. Also tried going rich and leaner on the tune up and neither helped.
Finally decided to swap springs, used some pacs....they were doubles. Can't remember what part # but I called BTR and he was out of stock of his springs and recommended the PAC springs to me instead.
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 Just ordered BTR PAC 1905's.. For some reason I have a feeling its my springs ..gonna get them in and drop it off at my tuners ,hopefully he can figure it out possibly turn the boost up
I'd like to push this 5.3 to its limits but first have to get it to operate correctly lol...thanks fellas for all the input ,its greatly appreciated ..I'll update as soon as I have the culprit to this madness!! Cheers!!
I'd like to push this 5.3 to its limits but first have to get it to operate correctly lol...thanks fellas for all the input ,its greatly appreciated ..I'll update as soon as I have the culprit to this madness!! Cheers!! 
On The Tree
Joined: May 2012
Posts: 175
Likes: 0
Valve springs usually just quit pulling rpm/making power and level off, not so much backfiring/popping/missing. You can drop the boost and see if it pulls more rpm, if it was a crank sensor I wouldn't think it would care about boost, but doesn't help to eliminate plug gap or coils.
TECH Resident
Joined: Sep 2013
Posts: 993
Likes: 119
From: Mechanicsburg, PA
I have had valve springs cause a misfire/backfire. I had never seen that before in 30 years of building/repairing/racing. Like turboventura said, they usually just lay over at high rpm. It also made the wideband dance full lean just like a spark misfire.
Teching In
Joined: Jul 2014
Posts: 30
Likes: 0
From: Arab,al
Valve springs is what it sounds like. Boost on the back side of the valves will cause the valve to want to open "or not close" which makes you need stronger springs then with n/a motors. If you get valve float your wide band is going to read alot different when it happens. I had an egt probe and it would go from 1400degs to 1800degs. The pistons survived but the spark plugs didn't. Burn ground staps off. Just a suggestion. Could be wrong.