2000 G20 misfiring when I start the car

[2000g20]

I just bought a used 2000 G20 with 100,000 mi. Most of the time it sounds fine, but sometimes when I start the car it starts misfiring and driving rough. This continues until I drive the car a couple of miles then it stops and drives ok until I restart the car. It doesnt do it everytime, but it was doing it a lot when it got really hot out (mid 80s and up). Its also worse if I start the car with the air on.

I only have a few more days to exchange the car but the weather has cooled off (70s) and its not doing it anymore. My regular mechanic cant figure it out. Does anyone know if this is potentially a serious (and expensive!) problem or is it more likely bad plugs or bad gas or something minor? I havent taken it to the Infiniti dealership mechanic yet because its not been acting up but Id hate it if it got really bad as soon as I could no longer exchange it. Advice anyone?!? Thanks!

[nametakennow]

Since it only happens when it's warm out, I'd say it's something minor. Have you filled it up since you bought it? Could be that the gas was old.

Anything major would probably throw a code. I assume your service engine soon light is not on.

[gumbyp10]

do a full tune up, and get your battery and alternator checked, it happened to my 96 but i never had time to fix it completely before i crashed it

[lcurran429]

I'm having a similar prob with my B15. I was reading up on it, and discovered my miss is caused by a bad head gasket. A dead give away is if your coolant level is going down. Not all misses are caused by HG, but as I said "if the coolant level is going down, your head gasket might be letting coolant leak in to one or more cylinders, causing a miss at start up. If your coolant isn't leaking, it's probably something else. I bought an extended warranty, but my dealer bites. I'll be hard pressed getting them to fix it. So I'll probably be wrenching myself. Wondering if anybody's tried the new sealers you pour into the radiator. Wishful thinking on my part!!!!