I have an LS1/T56 from a 2001 Camaro swapped into an older Corvette. Moderate build: 383, heads, 222/226 cam, stock TB (cable)/MAF/Intake/PCM. Swap was completed in 2021 and was tuned at that time by a local-ish tuner with a good reputation. I race in local autocross events and it was fantastic, never had a single issue.

I recently put in a larger 226/234 cam and ATI 10% ud damper then got it re-tuned by the same tuner. It runs and drives great but now it dies completely whenever I rev it to about 6300 rpm. I don't have logs and my old tach is off a bit so 6300 is my best guess of actual engine rpm. Fuel cutoff is 6500.

It will do this ~90% of the time when revving that high, whether it's accelerating in gear or just free revving. I believe it dies when I let off, but that could be a coincidence since that's when I would be letting off anyway. It always fires right back up but requires a key cycle - I've had to do this on course and can still get good times if I'm quick enough restarting it. If it's in gear and the car is moving the engine will continue to rotate and the tach confirms that. This tells me the PCM is a) alive, b) receiving crank signal, and c) transmitting RPM.

The tuner has been great to work with and engaged on solving this issue from his end. He doesn't see anything obvious in the tune file that would be causing this and is willing to take a look in person, which I'll likely end up doing. Before spending the better part of a day fighting traffic to do that I figured it couldn't hurt to ask the internet.

Has anybody experienced something similar that could point me in a direction to look? What would cause the computer to NOPE out at high rpm, any sensor going out or bad connection that might be causing this issue?

 

Since your RPM guess is not too far off from fuel cutoff, it could be that is the issue???

Nick

 

I'm going to guess the fuel pump

 

Put a fuel pressure gauge on it and see what your pressure reads.

 

It really seems fuel related, possibly rev limiter related. I have a basic OBD reader and the PCM is commanding spark even after the engine dies at high RPM. It can only read fuel trims; there's no fuel pressure sensor for the computer to know directly what's going on with that system. It doesn't sample fast enough to determine the exact RPM unfortunately.

It behaves the same whether it revs up quickly or gradually, under load or not, and letting off the throttle or staying in it. It's like it bounces off the rev limiter once but never recovers.

If it was the fuel pump would that cause the computer to completely shut down the engine? Wouldn't it just lean out then come back once the rpms drop?

 

Are there any OBD2 fault codes?

 

Nope, all clear.

 

Problem solved: appears to have been a corrupted file transfer. Tuner re-flashed the same tune and now everything works. Thanks all.

 

That doesn't sound plausible. If the file is corrupted, the PCM won't boot.
I went through that a few times while screwing around with my own PCMs.

 

Maybe it was a bad transfer, maybe it was something else. All I know is he hooked up his laptop for no more than a couple of minutes and it's fixed now.