This one has me stumped. Car sat outside all winter (fuel pump quit) Had fuel pump and filter replaced two weeks ago - when I picked up the car from the shop, it started and idled fine until I got about 1 block away, then it was acting like the ECM hadn't gotten
itself dialed in yet(loss of power,part throttle stumble,dies at idle) I drove it on city streets out to the freeway about 4-5 miles - this is usually enough drive time to reset the ECM - if I shut the ignition off and restart right away it runs fine for about 20-30 seconds,
then starts missing,stumbling,etc. Full throttle is fine, doesn't skip a beat. I have tapped hard on the ECM(no effect) disconnected the MAF(no effect)Seafoamed it through the vacuum line in the throttle body - poured the last half of the Seafoam it the tank,thinking I
may have a sticky injector. I haven't yet checked the connector to ignition module(remember car sat outside all winter-under the hood it shows),haven't checked IAC yet,
or EGR. Will have some time this weekend to do some more troubleshooting. Am I
missing something obvious? I want this car running right as I am planning on selling it.Car ran perfect last fall B4 fuel pump quit -had just done new coil pack,plugs,wires. No codes
set by ECM. Anyone have any ideas? Thanx.

The idle changing after 20-30 seconds has me thinking O2 sensor. The first 20-30 seconds the engine runs without the O2 sensor and then stitches to real time data.

I also am thinking bad gas, as it has been sitting all winter. Run it down, and fill it up. See how it is doing after 2-3 tanks.

x2 with rj, gas dont like sit for too long, you could throw some stabil in it and fill it with fresh hopefully it will come around

Thanks everyone for the input, Hopefully I will have it fixed this weekend, will post when I have more info.