LS7 stalls after crank
01-01-2013, 04:23 PM
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LS7 stalls after crank Hi there, wanted the opinions of the LS1Tech collective For a problem I've been having with my LS7.
Would greatly appreciate any assistance provided.
Issue
Car is a stock internals LS7 in a C6Z with headers, tune, ported intake and manifold.
Upon initial crank over, the engine starts up with the engine being louder than usual (as if it was revved), then quickly stalls. I am able to repeat the condition and unable to get the car started. Sometimes a little exhaust smell, but no leaks or hole in the block.
Not longer than 2 hours before it first happened that I was driving it around town, testing out my new Go Pro camera. Got near 7k a few times but it ran like a champ and when I parked it it was just fine.
Giving it some throttle during the start up process seemed to keep it alive momentarily, but very very rough idle and would stall shortly after.
Car shows a P0106 code... 'Manifold Absolute Pressure (MAP) Sensor Performance'
Troubleshooting Performed -
Pulled the valve covers and all of the valve springs and valves were still in there rightful place. Nothing obviously wrong.
A member on the Corvette forum with a C6Z was kind enough to stop by to help troubleshoot and used his C6Z to swap a few parts around.
Changed out the MAF sensor.
Changed out the MAP sensor.
Changed Throttle Body.
Checked Fuses.
Verified Fuel present from schrader valve.
Reverted to OE Tune.
Disabled P0106 code.
Read PCM via HPTuners
Verified exhaust output (incase of clogged cat)
Nothing seemed to get the car to start successfully. Any part we threw into the other car still worked just fine. Any part we moved to mine would still fail.
Probably attempted to start the car 20-30 times now. All the same result.
The Kicker
After some digging, we found the ported intake manifold has a 1" diameter hole in it. As a part of this porting process, a hole was drilled to remove the vertical columns then filled in and smoothed out with some sort of filler. The filler lost adhesion with the manifold and fell on top of the valley cover. The shape of the filler and the size of the hole did not allow the engine to pull it in. I'm working with the vendor/shop to exchange.
I figured this part was causing a vacuum in the intake which would explain the P0106 error, revs on startup, and failure to continue running.
However, I tried to seal the hole with some elaborate layers of duct tape (woo!) to see if it would help. Even though it appeared to have stuck (should have removed the vacuum), the car still won't run or idle.
So while the intake manifold is a problem and going to get swapped, I'm not 100% convinced its the root cause of this issue. Could be, but less sure than I was when I first found the hole.
Any ideas? Thanks again.
Would greatly appreciate any assistance provided.
Issue
Car is a stock internals LS7 in a C6Z with headers, tune, ported intake and manifold.
Upon initial crank over, the engine starts up with the engine being louder than usual (as if it was revved), then quickly stalls. I am able to repeat the condition and unable to get the car started. Sometimes a little exhaust smell, but no leaks or hole in the block.
Not longer than 2 hours before it first happened that I was driving it around town, testing out my new Go Pro camera. Got near 7k a few times but it ran like a champ and when I parked it it was just fine.
Giving it some throttle during the start up process seemed to keep it alive momentarily, but very very rough idle and would stall shortly after.
Car shows a P0106 code... 'Manifold Absolute Pressure (MAP) Sensor Performance'
Troubleshooting Performed -
Pulled the valve covers and all of the valve springs and valves were still in there rightful place. Nothing obviously wrong.
A member on the Corvette forum with a C6Z was kind enough to stop by to help troubleshoot and used his C6Z to swap a few parts around.
Changed out the MAF sensor.
Changed out the MAP sensor.
Changed Throttle Body.
Checked Fuses.
Verified Fuel present from schrader valve.
Reverted to OE Tune.
Disabled P0106 code.
Read PCM via HPTuners
Verified exhaust output (incase of clogged cat)
Nothing seemed to get the car to start successfully. Any part we threw into the other car still worked just fine. Any part we moved to mine would still fail.
Probably attempted to start the car 20-30 times now. All the same result.
The Kicker
After some digging, we found the ported intake manifold has a 1" diameter hole in it. As a part of this porting process, a hole was drilled to remove the vertical columns then filled in and smoothed out with some sort of filler. The filler lost adhesion with the manifold and fell on top of the valley cover. The shape of the filler and the size of the hole did not allow the engine to pull it in. I'm working with the vendor/shop to exchange.
I figured this part was causing a vacuum in the intake which would explain the P0106 error, revs on startup, and failure to continue running.
However, I tried to seal the hole with some elaborate layers of duct tape (woo!) to see if it would help. Even though it appeared to have stuck (should have removed the vacuum), the car still won't run or idle.
So while the intake manifold is a problem and going to get swapped, I'm not 100% convinced its the root cause of this issue. Could be, but less sure than I was when I first found the hole.
Any ideas? Thanks again.
Last edited by Jawnathin; 01-01-2013 at 04:39 PM.
01-02-2013, 04:51 PM
#2
Sounds like a vacuum leak, which would explain the code from the map sensor. Duct tape isn't going to stop a vacuum leak
Other things to test, make sure the map sensor plug on the intake manifold isn't cracked and leaking.
My cam position sensor is going bad and causes my car to stall after starting till the computer switches to the cranks sensor. A bad crank sensor can cause the car to stutter and die while driving. Doesn't seem relevant but just a bit of insight
Grab some carb cleaner and spray it around the intake manifold while the car is running. Spraying it on an area with a vacuum leak will cause the car to stutter and identify your problem area
Other things to test, make sure the map sensor plug on the intake manifold isn't cracked and leaking.
My cam position sensor is going bad and causes my car to stall after starting till the computer switches to the cranks sensor. A bad crank sensor can cause the car to stutter and die while driving. Doesn't seem relevant but just a bit of insight
Grab some carb cleaner and spray it around the intake manifold while the car is running. Spraying it on an area with a vacuum leak will cause the car to stutter and identify your problem area
01-03-2013, 01:38 AM
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Thanks for your reply.
I do agree that the code is from the MAP sensor, due to this hole, but I'm wondering if its just a different problem and the root cause is somewhere else. I'm going to get the intake manifold replaced (waiting for one to come in) so I'll find out sooner or later. Just wanted to gather opinions in the mean time as I thought I sealed up the hole well enough to at least let the car idle.
The map sensor plug on the intake manifold is not leaking. I cleaned the sensor and the mounting area looked pretty good.
I'd like to try the carb cleaner idea, but the car won't run. It turns off right after getting cranked over. Also, the hole is on the bottom of the intake manifold and I cannot access it without taking off the throttle body.
Picture of said hole is attached.
I do agree that the code is from the MAP sensor, due to this hole, but I'm wondering if its just a different problem and the root cause is somewhere else. I'm going to get the intake manifold replaced (waiting for one to come in) so I'll find out sooner or later. Just wanted to gather opinions in the mean time as I thought I sealed up the hole well enough to at least let the car idle.
The map sensor plug on the intake manifold is not leaking. I cleaned the sensor and the mounting area looked pretty good.
I'd like to try the carb cleaner idea, but the car won't run. It turns off right after getting cranked over. Also, the hole is on the bottom of the intake manifold and I cannot access it without taking off the throttle body.
Picture of said hole is attached.
