2005 Kia Optima 2.4 L 4 Cyl with 97,xxx miles This is a weird problem that's been happening for two years now. Why have I let it go for two years? Because, oddly, it's seasonal. It will happen in the autumn and the spring. All I can figure it it's temperature related somehow, as it happens when it's chilly (like 50ish) but not warm/hot or cold. There are no CEL's What happens is I'll be driving and the car will shut off. The tach drops to 0 and I loose all engine-powered features, such as power steering and power brakes. It's as if I turned the ignition back to the ACC position from the ON position. Depending on speed, the car will usually start back up. But if I'm going slow (like backing out of a parking spot or pulling into traffic) it will roll to a stop and then I'll need to crank it over with the starter. I have no idea where to start. The ignition is on my list of suspect parts. My mechanic thinks the crank sensor. But from the lack of CEL I'm doubting that. But he is a mechanic and knows more than me. From reading various forums it seems like people are having a similar problem that traces back to the main relay, but all of them have been with Hondas and Mitsubishis. Right now I'm at a loss. Now that the weather is cooling off, I'm looking into troubleshooting it. It's so intermittent that the mechanic hasn't found anything, but it's dangerous enough that I need to fix it. If anyone has any troubleshooting tips, I'd really appreciate it. I don't want to randomly start replacing parts but I need to take care of this!