Just curious to see if anyone else has run into the same issue.

If my car sits for more then 10 hrs the car will fire up to around 1900 RPMs then fall to 8-900 running very rough for approx 10 seconds then pop back up to the normal warm up curve.

This phenomenon is exaggerated with dwell time between engine runs.

Unfortunately the issue occurs generally before the wideband O2s have warmed up enough to read. Below is a snap shot of my cipher capture.



I'm highly suspicious of a faulty fuel pump check valve allowing pressure to bleed off and the key on pump prime gets enough fuel to start and run but needs a few seconds to fully refill the line / rail.

Of course the fuel rail access adapter is ridiculous overpriced and not really worth buying versus replacing the fuel pump.