2004 Hyundai Sonata starts and then dies

Question

My aunt has a 2004 Hyundai Sonata. It's been running rough for quite a while (few weeks, months?) now - it seemed to coincide with her daughter hitting a huge pothole/bump.

She drove about 40 miles with no real problems, then let it run for a few minutes while sitting there. She went back out to the car and started it and it dies almost immediately.

It starts right up when you turn the key, runs for a couple of seconds, and then shuts off. It feels/sounds like you just turned the key off (i.e. it doesn't stumble and then die, it just dies right out when it dies).

However, if you hold they key past the "on" position (it doesn't have to be fully in the start position) it will continue to run. I kept it there for several seconds, could rev the engine, and it all seemed to run. It still ran rough while it was running, but it did run.

What could cause the problem, and worst case scenario would it damage anything if she drove with the key turned? I'm sure it would be difficult to drive like that, but we're currently at the hospital and she's trying to get home (about 40 miles).

(other information: it does leak/burn some oil, the check engine light is always on and last check over a year ago reported the O2 sensor, and some electronic thing was replace in the engine a couple of years ago. Nobody remembers exactly what that thing was, but it prevented the car from starting)

Answer 1

Try and take the key off any keychain that could be pulling on it. Heavy keys are the usual culprit here. After that I would check the wiring, but a mechanic may be better suited to that kind of diagnostic. You may need to replace the key and cylinder if they are damaged, though a locksmith may be able to repair it.

Answer 2

She had a mechanic take a look at it - the problem ended out being the camshaft sensor.

Answer 3

I can be pretty confident in saying that it must be worn/dirty ignition switch contacts.

You should be able to remove the cowl around the steering column to get access to the rear of the ignition switch barrel. From there you can usually remove the switch mechanism off the rear of the ignition switch. There is also usually a connector that allows you to completely remove the switch from the wiring harness.

From here, you could either spray some switch cleaner inside it, disassemble the switch and clean it, or replace the switch.

Disconnect the battery negative lead before starting this procedure.