Engine Rumble Issues! Help!
 

Hello all, (please note - I am stupid with cars...)

I have a 2005 Mazda3 2.0L (99k). My wife and I drove the car for about and hour today, did some shopping and came back out to the car and it wouldn't start or turn over at all. I popped the hood and noticed that one of the connectors to the batteryt was not connected. I grabbed a wrench, tightened it up, and then pushed it back on. The car started right up.

However, after doing this, there was a pretty big rumble in the engine while the car was in park. When I put the car in drive the rumble got worse. Also, the rumble was intermittent - it would rumble for 1 second, the rpm's would rise slightly, and then the rumble would die down for 1 second, and the rpm's would subside slightly- and it would repeat like this constantly (this is all while the car is in park, but the rumble was worse when I put the car in drive with my foot on the break). I drove the car back home (about an hour drive) and on the highway it was great. I didn't notice a rumble and the rpm's were consistent. However, when I got off the highway, and came to a stop light, the rumble came right back up again, and this time the car completely quite (I was still in drive with my foot on the break while at the stop light). I started it back up again, which it had a hard time doing and got it home.

Does anyone have any idea what might be going on with my car? I would appreciate any thoughts!

Thanks!

scott

First make sure there aren't other connections that are bumped off, i'm not sure how the battery connection could have come loose.
Next thing to try is disconnect the battery again, it sounds like something may not have reset properly. "they" say do disconnect for 30 seconds, but I'd bet that 10 sec would be plenty.
If that doesn't work it sounds like the idle air control - though I don't recall what parts are involved on this car.