Newbie needs Diag help, LS7 starts then dies, starts then dies

[thorped]

2013 LS7 with tune. Car ran fine, then about 20 miles after re-fuel, engine started sputtering and died, restarted it while coasting and revved it for a second, then it died. Had to pull off the side of the road, it would restart but immediately die. Had to trailer it home, and could not work on it due to job, but I have some time now.

Thought it might be a bad fuel pump, but checked rail pressure and read about 50 psi, which I think is good. Connected VCM Scanner and got the attached data. The data is for three starts (three tries), and is just for a few seconds. I'm not sure if the data points to an issue, but thought someone more knowledgeable that me could quickly tell if there was a problem.

There are no DTCs, except for P0420 - Catalyst System Efficiency Below Threshold (Bank 1) (Permanent), and P0430 - Catalyst System Efficiency Below Threshold (Bank 2) (Permanent). Not sure why these are there but I think that I might be running rich from the shop tune.

I'm going to swap out the fuel, in case I got bad gas, but again, car ran fine for at least 20 miles after the refuel. When the problem first came on, it was quick, so I don't think it's the fuel. The problem (starts then dies) is so consistent that again I don't think it is the fuel. I'll advise after the fuel swap. Any help/suggestions with the log file would be appreciated.

Dave.

[gtstorey]

Is this in a swap or in an oem vehicle?

[thorped]

OEM. Car has ran good for many months with current tune until this issue.

[GHuggins]

Make sure you didn't suck something up into the MAF. It's reading oddly with high airflow then low then back high then back low. See if it'll run with the MAF unplugged or set the tune up to fail it and see if it'll run. It's most likely a MAF only tune, but should run on the factory VE. Inj pw is really low. I assume AM injectors?

[gtstorey]

Isn’t 50psi on the low side? I would have assumed this should be 58psi but maybe not.

[GHuggins]

Isn’t 50psi on the low side? I would have assumed this should be 58psi but maybe not.

This is a strong point. Check it with key on and while trying to run. It should stay at 58ish psi. With things reading goofy and it just killing over like shutting the key off, it even makes me wonder if a power or ground cable came loose or burnt up. Cover all of your bases and go from there.

[thorped]

All,
Merry Christmas and tks for the help...problem solved!

I replaced the MAF and it fired up and kept running. Going to take it for a long test drive now.

Just wanted to say that the comments were helpful, unlike some that I've seen on other forums. I think that "HP Tuners" folks are more knowledgeable than the average "car guy" and I appreciate the help. Special tks to Greg whose comments pushed me to look at the MAF values closer and take a shot at replacing the MAF!

R/
Dave.