Engine goes lean, only on downshift (Auto)

[redmist]

I have my car fairly dialed in I think. I can stab the throttle from a stop, and it spins the tires nicely. Free reving is great, car drives great, running through the gears is great... However!

Tonight I stabbed the throttle for the first time at cruise 20MPH or so, and the car downshifted, engine RPM went up, then car just stopped like a fuel cut. Got home, pulled the log and this is what I see.. What is causing this massive lean spike??

[Matt Cramer]

Check to be sure it's not your fuel pressure dropping.

[rrrobert]

fuel surge in tank uncovering pickup?

[redmist]

Thats possible I suppose, I am running an Aeromotive phantom 340 setup with the foam and sump that comes with the kit. It should take a long while for it to uncover.

I noticed my VE map goes flat at that exact point in my logs, I scaled it to increase beyond that and will retest.

[kaeman]

Don't rely on the foam to do anything except plug a fuel filter, especially if you are using fuel in California, I had the foam filled tank and my rear sump pickups lost suction if I applied the brakes to hard.... the foam didn't stop the fuel from moving away from the pickups in my tank, I removed the foam and the fuel returned to the pickups quicker, the datalog looks like its running out of fuel pressure, the other thing is that the lean started happening before the shift point.. did you have an ignition problem, because a rich miss fire will show way lean also and cause the engine to fall on its face for a second.
How full was the fuel tank when this occurred.
Good luck