My wife picks up her car from the shop yesterday after having a rear wheel ABS sensor replaced and says it idled rough and acted like it was going to stall. She gets it home and then tries to go to the store and it starts, shakes and stalls right out. She tries it like 3 times with same results. I get home later that day and it starts and idles perfectly, take it for a drive, everything seems fine. Any ides what could have happened??

how many miles? last time plugs were changed? is it a 3.0?

I think the problem was the spare keys were under the front floor mat and some how activating the immobilizer system. They were right were she normally rests her left foot. The car has run perfectly ever since, no stalls or hiccups. Tell me if I'm crazy!!

That happened to my car a few months back. I would start my car and it would idle rough and sometimes stall. Some days it would start up perfectly but sometimes it would idle rough so i changed the plugs and wires everything was perfect after that.