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Lm7 rough start then stalls?

Tiny
RALPHIEADAMS
  • MEMBER
  • 2003 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 85,000 MILES
I fully rebuilt a lm7 (followed your YouTube videos, you are awesome by the way). Installed it with a 4l60e into my 1970 Toyota Landcruiser FJ40.
Used the original wiring harness, used an OEM fuse box, etc.
Got it to turn over and fire up but the engine runs for a few seconds at a very low idle and then shuts off. The rpms don't get about 500ish RPMs (typically around 300-500). I have done a smoke test on the intake, no leaks found. Installed a new throttle body (original one was well used and dirty surfaces even after cleaning). Fuel Pressure about 55 PSI during cranking. I have not replaced the crankshaft or camshaft sensor (maybe my next steps?)
Thoughts?
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Saturday, January 6th, 2024 AT 4:05 PM

1 Reply

Tiny
RYAN L
  • ADMIN
  • 256 POSTS
Hey, thank you so much for watching the series!

Yeah, my "go to" on intermittent stalling is the crankshaft positioning sensor. I would also check and make sure your MAP sensor is fully seated and plugged in. That can also cause it.

If you have a scanner that can see what the engine is doing and receiving from the sensors that would be a big help.

Thank you for using 2CarPros!

Best,
Ryan
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Monday, January 8th, 2024 AT 2:19 PM

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