Hey guys. in the last 48 hours, my car has had a weak battery. its been fine all winter. I first noticed yesterday leaving work when the car didnt have enough juice to get the engine started. I have no accessories plugged in except for an iphone via 5pin connector. (it has never caused an issue). The last time I worked under the hood was 3 weeks ago to install a plenum kit. I disconnected and reconnected the battery. Both terminals are tight. The battery has to be jumped at every start now. its always just shy of ignition on its own.

Does anyone have any ideas what the problem is? The car is stock except for the kit. I'm hoping to get this knocked out before Auto X this weekend.

 

Once it starts it runs fine though?

If so, the battery is just dying. Cold winter isn't nice to batteries.

 

First, check to be sure the battery terminals are both clean and tight.

If you have a voltmeter, you can do some simple tests. Check the voltage of the battery with the ignition off after the car has been sitting for maybe an hour. Voltage across the battery should be 12.7 or a bit more. Start the car and check the voltage on the battery again. Should be 13.8+, and probably a bit over 14. Very basic, and this doesn't actually check the load capacity of the battery, but it will show that the alternator is charging. Any auto parts store should have a free service to do a more in-depth test.

Sounds like you need a new battery, though. Spend the $100 and be done with it.

 

I concur- particularly if the battery is more than five years old. That's about the limit for service life of a battery in the Z.

 

Turns out it was the battery. I had it tested at sears and it was only working at half capacity. Thats funny because the battery practically went bad over night, which is a first for me. And it cranked fine all winter. Anyway I had a new one put in and I'm good to go.
Today I'm getting my Hankook Ventus V12's mounted

 

Also when you get your new battery, invest in a Battery Tender.

 

Why? - sounds like this car is a daily driver.

 

During cold months or periods when he isn't driving the Z, why risk the battery dying?

I do not daily drive my Z but it is a 2005 that only had the original battery replaced. Plus once you connect the quick disconnect to the batter terminals, it only takes a few seconds to unplug it and be on your way.

Edit: Peace of mind for $20 some odd dollars.