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1993 sc400 start stall after ecu repair

  • Antman
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3 years 19 hours ago - 3 years 18 hours ago #58262 by Antman
1993 lexus sc400 v8 1uz fe engine 4spd auto
Some repair history:
Original complaint was vehicle stalling when first start
but once warm it runs fine minus some rpm bounce. Found isc valve was getting no power or signal. Found the ecm was putting out a weak 12v where it should be grounding the isc valve. Also found an open under the intake manifold because the 12v from the ecm wasn't making it to the valve. So the fix was repair the harness and send the ecu out for repair as it had capacitor damage all over the board.

One week later and repaired ecu installed: Vehicle starts and then stalls within 1-3 seconds. Opening the throttle seemed to make it die faster and I noticed it was low on fuel so I added 2 gallons of regular but no
change. Still suspected a fuel issue so I bypassed the fpcm
and still no change. You can here the fuel rushing through
the rail so I know the pump is at the very least turning

Put a scope on to see if I can catch whats not working but
I'm not too proficient in it yet. I believe the high spike
in the spark line indicates a low fuel condition and the
injector signal also seems strange to me as it has
occasionally very low spikes but a current ramp shows
Pintle movement. Haven't checked fuel pressure yet since it requires a special adapter that I had to order

Going to smoke test the intake tomorrow but nothing has
been messed with besides the harness for the isc valve
since the ecu went out for repair a week ago and it ran
just fine minus the lumpy idle.

No flash codes or anti theft either. Any ideas are very
much appreciated. Thankyou for reading

Yellow-injector signal
Green-coil
Blue-injector current
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Last edit: 3 years 18 hours ago by Antman.

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