I drive a Mitsubishi Outlander 2007, V6, about 300,000km.

I had just replaced the spark plugs a few weeks ago, and a few days ago the ignition started to sound very weak, taking upwards of 3 seconds to start when it usually takes less than 1 second. This happens after leaving the car for long periods of time (8+ hours), even in the dreadful heat of summer (Toronto).

So I replaced the battery and it was OK for a few days, then the same problem started happening again, in fact it got so bad that I could not start the car at one point. It coughed a couple of times then wouldn't start at all.

However, turning off the radio allowed the car to start. Anyone have ideas?

AC was off when I tried starting, I will turn the key to power car electronics, turn off AC, then try again.

 

I'd start with having a parts store check battery and the alternator...could be a coincidence.