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I bought a 13 grandsport with a bad motor. Swapped a crate ls3 in it. Car cranks and runs fine but under hard acceleration computers dies and car must be restarted. It did it with the tuner and he felt a ground was loose some where.Checked all grounds, replaced bcm,fuse box under hood , put new optima battery in. Still does it. Battery is in rear of car , it seem to do better after I cleaned the battery connectors real good but went right back to dying. Any help would be appreciated.
Last edited by billy25us; Jul 14, 2021 at 10:36 AM.
Reason: Mistype
I'd start by tracing all of the big wires from start to finish. Pay special attention of the ends where the insulation stops and the connector starts. I've seen the ends of battery cables corrode under the insulation. Looks perfectly fine. Skin a little of the insulation back and you see corrosion and dust. That or a hot wire grounding occasionally from a small break in the insulation. That cable from the battery in the back to the front is long and has lots of potential for trouble. Any kind of interruption of current will drive the electrical system bat **** crazy. The engine moves a little under hard acceleration.
Without a scan tool and a scope you’ll be chasing your tail with kind this issue..you’re better off taking the car to a diagnostic shop (not a repair shop) and let them look at it…they’ll hook a scope up to the car while driving looking at a few sensors and also data from the scan tool to see what’s dropping out…fuel pressure, crank/cam sensor, fuel injection or spark.
Without a scan tool and a scope you’ll be chasing your tail with kind this issue..you’re better off taking the car to a diagnostic shop (not a repair shop) and let them look at it…they’ll hook a scope up to the car while driving looking at a few sensors and also data from the scan tool to see what’s dropping out…fuel pressure, crank/cam sensor, fuel injection or spark.
You are correct. My partner owns a full service center. Its been on a tech2, snap on portable with latest software scanner, and the tuner had it street tuning. Unfortunately it sets no codes, and is intermediate at times. Our cost on bcm,and fuse block was only couple hundred bucks a peice so we were ruling out a random relay. Or something enternal in bcm. When I say car dies , more specific we lose 12v car will restart immediately.
Does your partner have a scope ???….if he owns a full service center he should !!…you are not going to find the fix for this with only a scan tool…now when you say you lose 12 volts where are you losing it ???…that’s why using a scope is essential in finding the cause of this…if not you’re just guessing and that can get expensive !!
[QUOTE=C5 Diag;1603734841]Does your partner have a scope ???….if he owns a full service center he should !!…you are not going to find the fix for this with only a scan tool…now when you say you lose 12 volts where are you losing it ???…that’s why using a scope is essential in finding the cause of this…if not you’re just guessing and that can get expensive !
Help with LS3 dying Under hard acceleration?
