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LS1 shuts down while cruising around 60

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Old Jul 10, 2015 | 02:38 PM
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Default LS1 shuts down while cruising around 60

This is an LS1 swap into a Brunton Stalker. I have done this swap many times with all kinds of LS engine and never had a problem like this.
When cruising around 60 mph or above, the engine will randomly shut down. It takes a complete computer reset (or disconnect of battery) to get it to start again. It doesn't do it at lower in the city speeds. We have tried tricking the ECU to think it's going slower with the VSS pulses but still have this issue.
The ecu is a Stock 2001 LS1 tune (as far as I know, bought used)
The VATS is disabled.
What kind of conditions could cause the computer to shut down completely and not want to start again?

Scott
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Old Jul 10, 2015 | 02:45 PM
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I would be curious to know what exactly shuts it down. Does the pcm stop communicating with scanner? Does it have fuel singal or spark? Fuel pressure? Do you have any circuit breakers installed anywhere?
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Old Jul 11, 2015 | 05:47 AM
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Do Fault codes/Freeze Frame data tell you anything?

If not look for Voltage drops or ground issues. In my experience when strange things are happening those tend to be a cause. As rpm increases demand on the electrical system increases to power the coils and injectors. This might explain why it is only a problem at higher speed.

If you are sure everything is fine try a different PCM as there could be a board/component level issue internally.
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Old Jul 11, 2015 | 06:33 AM
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Data log???
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Old Jul 11, 2015 | 08:50 AM
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Could just be a bad ECM.. have you tried swapping it for another or having it re-flashed ?

keep us posted.. as I think many will want to know what the cause is.

BC
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Old Jul 16, 2015 | 08:29 AM
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I am getting the car back here soon to fix and try out some testing. Trying to study up before I get it back here.
When I say the car shuts down, it just stops running. Electrical systems still work. Fuel pump still turns on, ect. throwing NO CODES.
What is weird is that the ECU needs to be reset with a scanner, or disconnected form the battery to restart the car. Is there any kind of sensor that could intermittenly fail and cause this?
Whats interesting is that it is not a load issue. It only happens when cruising, almost no load at around 60 or above. You can accelerate hard as hell through high speed with no issue. I will get a datalog asap. Just wondering if anybody knows what kind of sensor failure would cause a total shut down and not allow a restart until cleared.
I guess first thing is to try a reflash with a known good tune, from there, a new ecu.

Scott
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Old Jul 16, 2015 | 09:52 AM
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Nothing sensor wise I know of that would kill it without a code.

If power circuits are perfect I would get a different PCM.
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Old Sep 3, 2015 | 03:00 PM
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Torque Converter Lockup? Lean Cruise? Fuel Trims?
Maybe a short in one of these systems is feeding back to the ECU and causing it to freak out.

Did you ever get this figured out?
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