Working great…until it wasn’t
Thread Starter
Teching In
Joined: Dec 2024
Posts: 15
Likes: 2
Working great…until it wasn’t I have a boosted 4.8 running a speed density tune and p59 ecu. It’s been running without any changes for years flawlessly. Was driving today nice and easy, and while stopped at a light it just died. When I tried to start it, it kinda ran, but sounded like it was hitting a limiter at 2k rpm and super rich, and wouldn’t idle without pedal input. Tried to crank a bit more and battery died (was weak but charging system works fine)
Now while boosting it, it’ll run for a split second and then die, and it’s consistent, almost like VATs is disabling it, even though it was deleted. Fuel pressure good, no vac leaks, intake not plugged up, no blown fuses, didn’t get hot.
But while scanning, it’s not failing the maf codes, wondering if that could be the issue? Or it’s a computer issue out of the blue. Can they just fail? Kinda at a loss at where to start with this one.
Now while boosting it, it’ll run for a split second and then die, and it’s consistent, almost like VATs is disabling it, even though it was deleted. Fuel pressure good, no vac leaks, intake not plugged up, no blown fuses, didn’t get hot.
But while scanning, it’s not failing the maf codes, wondering if that could be the issue? Or it’s a computer issue out of the blue. Can they just fail? Kinda at a loss at where to start with this one.
I have a boosted 4.8 running a speed density tune and p59 ecu. It’s been running without any changes for years flawlessly. Was driving today nice and easy, and while stopped at a light it just died. When I tried to start it, it kinda ran, but sounded like it was hitting a limiter at 2k rpm and super rich, and wouldn’t idle without pedal input. Tried to crank a bit more and battery died (was weak but charging system works fine)
Now while boosting it, it’ll run for a split second and then die, and it’s consistent, almost like VATs is disabling it, even though it was deleted. Fuel pressure good, no vac leaks, intake not plugged up, no blown fuses, didn’t get hot.
But while scanning, it’s not failing the maf codes, wondering if that could be the issue? Or it’s a computer issue out of the blue. Can they just fail? Kinda at a loss at where to start with this one.
Now while boosting it, it’ll run for a split second and then die, and it’s consistent, almost like VATs is disabling it, even though it was deleted. Fuel pressure good, no vac leaks, intake not plugged up, no blown fuses, didn’t get hot.
But while scanning, it’s not failing the maf codes, wondering if that could be the issue? Or it’s a computer issue out of the blue. Can they just fail? Kinda at a loss at where to start with this one.
Thread Starter
Teching In
Joined: Dec 2024
Posts: 15
Likes: 2
I’m still seeing RPM signal, so crank seems ok, but potentially cam sensor. I’m running out of sensors to try. Ignition tumbler maybe? Key doesn’t seem wore out.
As I keep digging into it, it seems like something it shutting it off since it’s so consistent. It does seem like VATs, but it is switched off (running great for 5 year with no changes).
As I keep digging into it, it seems like something it shutting it off since it’s so consistent. It does seem like VATs, but it is switched off (running great for 5 year with no changes).
TECH Enthusiast
Joined: Feb 2020
Posts: 734
Likes: 209
I'm running p59 and SD tune , early the tuning process one of the narrow band O2s quit out of the blue and it went quite rich and ran terrible, easy diagnosis with hpt or a scan tool . I'm sure you checked that already but it happened to me so thought I'd mention it
Thread Starter
Teching In
Joined: Dec 2024
Posts: 15
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Yeah I’m not running any o2 sensors. But thanks.
Thread Starter
Teching In
Joined: Dec 2024
Posts: 15
Likes: 2
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Verdad Gallardo Thread Starter
Teching In
Joined: Dec 2024
Posts: 15
Likes: 2
Update. Turns out it was the MAP sensor. I replaced it with a GM 3 bar brick style I had sitting around (updated tune for linear and offset), and it fired right up.
2nd failure using the EFI source 3 bar sensor…
2nd failure using the EFI source 3 bar sensor…