Have a '92 RS with a 3.1 automatic and 148K miles. Started fine, pulled out of parking lot onto main road, went about a block, then died and won't start. Cranks strong and I can hear the fuel pump running. Has been running well in cold weather after warming up for a minute or so - without that warmup, it would stumble or occasionally stall, but start again with no problem. Any ideas where I should start troubleshooting?