Yes, I wondered why it stalled too. There have been many abductions or attempts where a woman's vehicle malfunctioning is part of the reason why. This could legitimately be due to fluke (ie. an abductor just happens to be around when the car trouble starts) but then there's been some noted cases where the individual who shows up to help actually caused the car trouble.
Graham ran out of gas right? Siphoning? Her car was parked at work. I wonder if someone she worked with siphoned her gas and followed her. It would explain why she might trust him.
I wrote about this topic.
Women With Car Trouble Go Missing.