Please help beware long thread
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
Please help beware long thread So! I bought a ls swapped s10 5.3 fitech 750hp kit with 4l60e was twin turbo now just all motor with cam Elgin sloppy stage two so I was told.
I drove the truck for two weeks with zero problems then I went to start the truck heard a poof sound had an idea that it was a vacuum leak found 2 unsecured caps under the intake put the caps back on started truck then drove to work I went to start the truck again poof vacuums come off so I get clamps and put them
I start the truck it starts I try to take off it’s struggling and making a horrible sound so ofcourse at this point I’m convinced the vehicle is a pos
but I journey on I get ahold of the guy who built the truck heard tells me to check my afr reading one side was off
cool just a 02 sensor that’s easy I jack the truck up to discover the exhaust is completely loose I lightly jiggle it and it falls off the truck (not an exaggeration) literally falls off the manifolds onto the ground not a bad sensor just and exhaust leak
I fix the exhaust leak now we back in action runs great just like wen I bought it I get it home let it sit for a day the next day I start it up and drive it everything is great I go to start it after leaving the gas station I hear the poof again I check the hoses four roughly 6 hours looking for leaks until I broke down and got it towed home
next day I rigged a smoke test found a leak in the back of the intake my map sensor had been blown apart causing the vacuum leak which I found strange I replaced the map sensor go to start the truck as I’m cranking it I hear another loud pop
try again engine start but hold idle at2000rpm I check all my hoses again along the the brand new map sensor no leaks I can find so now I’m stuck PLEASE HELP IF YOU CAN
I drove the truck for two weeks with zero problems then I went to start the truck heard a poof sound had an idea that it was a vacuum leak found 2 unsecured caps under the intake put the caps back on started truck then drove to work I went to start the truck again poof vacuums come off so I get clamps and put them
I start the truck it starts I try to take off it’s struggling and making a horrible sound so ofcourse at this point I’m convinced the vehicle is a pos
but I journey on I get ahold of the guy who built the truck heard tells me to check my afr reading one side was off
cool just a 02 sensor that’s easy I jack the truck up to discover the exhaust is completely loose I lightly jiggle it and it falls off the truck (not an exaggeration) literally falls off the manifolds onto the ground not a bad sensor just and exhaust leak
I fix the exhaust leak now we back in action runs great just like wen I bought it I get it home let it sit for a day the next day I start it up and drive it everything is great I go to start it after leaving the gas station I hear the poof again I check the hoses four roughly 6 hours looking for leaks until I broke down and got it towed home
next day I rigged a smoke test found a leak in the back of the intake my map sensor had been blown apart causing the vacuum leak which I found strange I replaced the map sensor go to start the truck as I’m cranking it I hear another loud pop
try again engine start but hold idle at2000rpm I check all my hoses again along the the brand new map sensor no leaks I can find so now I’m stuck PLEASE HELP IF YOU CAN
Last edited by 7t7t/a; Apr 4, 2025 at 12:20 AM.
TECH Senior Member
Joined: Jun 2016
Posts: 22,291
Likes: 3,616
From: Central Cal.
So! I bought a ls swapped s10 5.3 fitech 750hp kit with 4l60e was twin turbo now just all motor with cam Elgin sloppy stage two so I was told I drove the truck for two weeks with zero problems then I went to start the truck heard a poof sound had an idea that it was a vacuum leak found 2 unsecured caps under the intake put the caps back on started truck then drove to work I went to start the truck again poof vacuums come off so I get clamps and put them
on so they don’t come off I start the truck it starts I try to take off it’s struggling and making a horrible sound so of course at this point I’m convinced the vehicle is a pos but I journey on I get ahold of the guy who built the truck heard tells me to check my afr reading one side was off cool just a 02 sensor that’s easy I jack the truck up to discover the exhaust is completely loose I lightly jiggle it and it falls off the truck (not an exaggeration) literally falls off the manifolds onto the ground not a bad sensor just and exhaust leak I fix the exhaust leak now we back in action runs great just like when I bought it I get it home let it sit for a day the next day I start it up and drive it everything is great I go to start it after leaving the gas station I hear the poof again I check the hoses four roughly 6 hours looking for leaks until I broke down and got it towed home next day I rigged a smoke test found a leak in the back of the intake my map sensor had been blown apart causing the vacuum leak which I found strange I replaced the map sensor go to start the truck as I’m cranking it I hear another loud pop try again engine start but hold idle at2000rpm I check all my hoses again along the the brand new map sensor no leaks I can find so now I’m stuck PLEASE HELP IF YOU CAN
on so they don’t come off I start the truck it starts I try to take off it’s struggling and making a horrible sound so of course at this point I’m convinced the vehicle is a pos but I journey on I get ahold of the guy who built the truck heard tells me to check my afr reading one side was off cool just a 02 sensor that’s easy I jack the truck up to discover the exhaust is completely loose I lightly jiggle it and it falls off the truck (not an exaggeration) literally falls off the manifolds onto the ground not a bad sensor just and exhaust leak I fix the exhaust leak now we back in action runs great just like when I bought it I get it home let it sit for a day the next day I start it up and drive it everything is great I go to start it after leaving the gas station I hear the poof again I check the hoses four roughly 6 hours looking for leaks until I broke down and got it towed home next day I rigged a smoke test found a leak in the back of the intake my map sensor had been blown apart causing the vacuum leak which I found strange I replaced the map sensor go to start the truck as I’m cranking it I hear another loud pop try again engine start but hold idle at2000rpm I check all my hoses again along the the brand new map sensor no leaks I can find so now I’m stuck PLEASE HELP IF YOU CAN
Your post is VERY hard to understand!
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
Teching In
Joined: Oct 2020
Posts: 40
Likes: 12
From: Calgary, Alberta
Trying doing a reset on your fuel learn and the idle learn. once you think all your vacuum leaks are fixed. I’ve been running a Fitech since 2019. I find it’s happy with a relearn every now and then.
You might need to play with your TPS as well make sure it’s not cracked more then it needs to be.
You might need to play with your TPS as well make sure it’s not cracked more then it needs to be.
TECH Addict
Joined: Dec 2017
Posts: 2,180
Likes: 969
The "poof" is backfiring into the intake; probably due to a lean condition.
Since the motor ran right at one time, the tune itself is probably OK. At least, not the first place I would look.
Vacuum leaks are a particular problem at idle and other high-vacuum situations. Obviously vacuum can't leak if there's no vacuum, such as at WOT or other high-load conditions. If your motor still has a MAF though, any vacuum leak or anything else that lets unmetered air into the intake, i.e. air that gets into the engine without passing through the MAF first, is "invisible" to the ECM; it has no idea that it's there, and can't possibly know to add fuel for it. That can create a lean condition as well. People hack their PCV systems and other things related to vacuum all the time and create problems of this sort. "Breathers" on the valve covers or elsewhere, with the PCV still hooked up, are a particularly common problem.
Exhaust leaks allow oxygen into the exhaust. Seems odd maybe, butt there's vacuum in the exhaust part of the time; that is, the pressure is below atmospheric, in between pulses of hot gases being expelled from cylinders. Air gets sucked into it at those times. The oxygen sensor senses OXYGEN, and NOTHING else; it does not sense "mixture", it does not sense "fuel", only OXYGEN. When the ECM sees oxygen in the exhaust as reported to it by the sensor, it is programmed to add more fuel; thus an exhaust leak will more often tend to make a motor run rich.
Your lean problem, which leads to backfiring, which leads to parts blown off of the intake, might be as simple as low fuel pressure. What does that measure?
Since the motor ran right at one time, the tune itself is probably OK. At least, not the first place I would look.
Vacuum leaks are a particular problem at idle and other high-vacuum situations. Obviously vacuum can't leak if there's no vacuum, such as at WOT or other high-load conditions. If your motor still has a MAF though, any vacuum leak or anything else that lets unmetered air into the intake, i.e. air that gets into the engine without passing through the MAF first, is "invisible" to the ECM; it has no idea that it's there, and can't possibly know to add fuel for it. That can create a lean condition as well. People hack their PCV systems and other things related to vacuum all the time and create problems of this sort. "Breathers" on the valve covers or elsewhere, with the PCV still hooked up, are a particularly common problem.
Exhaust leaks allow oxygen into the exhaust. Seems odd maybe, butt there's vacuum in the exhaust part of the time; that is, the pressure is below atmospheric, in between pulses of hot gases being expelled from cylinders. Air gets sucked into it at those times. The oxygen sensor senses OXYGEN, and NOTHING else; it does not sense "mixture", it does not sense "fuel", only OXYGEN. When the ECM sees oxygen in the exhaust as reported to it by the sensor, it is programmed to add more fuel; thus an exhaust leak will more often tend to make a motor run rich.
Your lean problem, which leads to backfiring, which leads to parts blown off of the intake, might be as simple as low fuel pressure. What does that measure?
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
Trending Topics
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
The "poof" is backfiring into the intake; probably due to a lean condition.
Since the motor ran right at one time, the tune itself is probably OK. At least, not the first place I would look.
Vacuum leaks are a particular problem at idle and other high-vacuum situations. Obviously vacuum can't leak if there's no vacuum, such as at WOT or other high-load conditions. If your motor still has a MAF though, any vacuum leak or anything else that lets unmetered air into the intake, i.e. air that gets into the engine without passing through the MAF first, is "invisible" to the ECM; it has no idea that it's there, and can't possibly know to add fuel for it. That can create a lean condition as well. People hack their PCV systems and other things related to vacuum all the time and create problems of this sort. "Breathers" on the valve covers or elsewhere, with the PCV still hooked up, are a particularly common problem.
Exhaust leaks allow oxygen into the exhaust. Seems odd maybe, butt there's vacuum in the exhaust part of the time; that is, the pressure is below atmospheric, in between pulses of hot gases being expelled from cylinders. Air gets sucked into it at those times. The oxygen sensor senses OXYGEN, and NOTHING else; it does not sense "mixture", it does not sense "fuel", only OXYGEN. When the ECM sees oxygen in the exhaust as reported to it by the sensor, it is programmed to add more fuel; thus an exhaust leak will more often tend to make a motor run rich.
Your lean problem, which leads to backfiring, which leads to parts blown off of the intake, might be as simple as low fuel pressure. What does that measure?
Since the motor ran right at one time, the tune itself is probably OK. At least, not the first place I would look.
Vacuum leaks are a particular problem at idle and other high-vacuum situations. Obviously vacuum can't leak if there's no vacuum, such as at WOT or other high-load conditions. If your motor still has a MAF though, any vacuum leak or anything else that lets unmetered air into the intake, i.e. air that gets into the engine without passing through the MAF first, is "invisible" to the ECM; it has no idea that it's there, and can't possibly know to add fuel for it. That can create a lean condition as well. People hack their PCV systems and other things related to vacuum all the time and create problems of this sort. "Breathers" on the valve covers or elsewhere, with the PCV still hooked up, are a particularly common problem.
Exhaust leaks allow oxygen into the exhaust. Seems odd maybe, butt there's vacuum in the exhaust part of the time; that is, the pressure is below atmospheric, in between pulses of hot gases being expelled from cylinders. Air gets sucked into it at those times. The oxygen sensor senses OXYGEN, and NOTHING else; it does not sense "mixture", it does not sense "fuel", only OXYGEN. When the ECM sees oxygen in the exhaust as reported to it by the sensor, it is programmed to add more fuel; thus an exhaust leak will more often tend to make a motor run rich.
Your lean problem, which leads to backfiring, which leads to parts blown off of the intake, might be as simple as low fuel pressure. What does that measure?
60 ps1
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 Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
Trying doing a reset on your fuel learn and the idle learn. once you think all your vacuum leaks are fixed. I’ve been running a Fitech since 2019. I find it’s happy with a relearn every now and then.
You might need to play with your TPS as well make sure it’s not cracked more then it needs to be.
You might need to play with your TPS as well make sure it’s not cracked more then it needs to be.
on the handheld my tps reads zero along with the iac
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
"on the handheld my tps reads zero along with the iac".
Vac leak or the throttle blades are too far open is my suggestion.
What map sensor did you put in?
What does the map sensor read key on/engine off?
Vac leak or the throttle blades are too far open is my suggestion.
What map sensor did you put in?
What does the map sensor read key on/engine off?
TECH Addict
Joined: Dec 2017
Posts: 2,180
Likes: 969
60 ps1
Sounds like you may have more than one malfunction going on. Sort em all out one at a time. See where that takes you.
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
I got the map for a 2007 ctsv map reads 110.5 kpa this was the direct cross from fitech
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
also this truck has 55lb injectors is that necessary for a cam only 5.3
TECH Fanatic
Joined: Jan 2009
Posts: 1,063
Likes: 475
From: Bostwick, GA.
Nope.... If you are not going to use the turbos, it's time to start over on the tune.
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
If you are not going to use the turbos, it's time to start over on the tune.
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?
it’s the 79009 750hp kit
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
[QUOTE=Old Buzzard;20604951]If you are not going to use the turbos, it's time to start over on the tune.
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?[/QUOTE
tge thing that is killing me is why did it run and drive perfectly for two weeks I just was going to work and home which is a 16 mile round trip at most then it just starts acting up
** The MAP should be changed to a 1 bar.
** instead of running the injs at 60, run them at 43.
What's the model number on the Fitech?
Some good pics of the set up would/could help.
You have the Fitech software on a LT?[/QUOTE
tge thing that is killing me is why did it run and drive perfectly for two weeks I just was going to work and home which is a 16 mile round trip at most then it just starts acting up
If its idling at 2k rpm and the tps and iac are both at 0% it's getting extra air from somewhere. It doesn't take as much as you'd think either.
Do you drive it around like that with no air filter on the intake?
Do you drive it around like that with no air filter on the intake?
Thread Starter
Teching In
Joined: Apr 2025
Posts: 10
Likes: 2
I drove it that way for a few days until I found a air filter that fit ran fine before and after I put it on found a vacuum leak yesterday capped it a hour ago still holding idle at 2k but now I have a iac code
There should be a hole in the throttle body in front of the blade on the top, it feeds air to the iac. while it's running you can cover that hole and see if it idles down. If it does then the iac is open. If it makes no difference your problem is elsewhere. It setting an iac code is the ecu basically saying the iac valve isn't making a difference, doesn't have to be a bad iac valve but it could be. A backfire like that will blow caps and hoses off, damage gaskets, sensors and even crack the intake. You can take flammable brake cleaner and spray it around anything attached to vacuum, if you hear the engine pick up or the o2 sensors go rich you have found your leak. IME with a big vacuum leak it can sometimes make the engine idle down when you spray directly on the vacuum leak, but when you spray the leak the engine should change in some way