I've had this happen a few times, only on the hottest of days and when the car's been driven a lot. I'm overwhelmed with exhaust in the car, and it doesn't matter if I'm moving or still, I can open the windows and air it out but I can still smell it. Windows up, it accumulates faster. Vents off, on, A/C off, on, it's all the same. I've even parked the car, never having smelled anything, only to come back hours later and have the car smell as if it's been running in a garage with a hose, suicide-style. It usually stops when the temperature goes down in the evening.

I've had the dealer check it out 3 times. The first two they found nothing and couldn't replicate the problem. Third time they smelled it and kept it for 2 weeks, then finally blamed it on the fuel pump access panel under the back seat, saying it had a corner bent up. I thought that sounded crazy, but didn't smell the smell again. Until now, when it's been hot again. I've looked around online but found nothing so far. Can you please HELP!!!??!?

 

could be an exhaust leak under the hood somewhere. my 96 has a pretty bad leak due to a crack in the exhaust manifold

 

I agree. Many times it's the flex hose in the exhaust but it could be a cracked or leaking manifold. Get it repaired quick. It shoudl still be under warranty Don't let the dealer just blow you off on this. It's a safety issue.

 

I'm having same issue. Check engine light came on less than 2 months ago codes were for rear o2 censor & small evap leak. Replaced censor & had gas cap Replaced. Light went off. Back on next day only 1 code for large evap leak. Took it back n they said it was gas cap again. Had a different one put on. Cleared codes and it came back on with same code. Large evap. Leak n a/c no longer cold air. Added freon today. Replaced yet another gas cap. Today was the first time ever smelling exhaust fumes inside car while driving & sitting still. Really strong, burning my eyes. My 3 yr old asked what the yucky smell was and of course light came back on again today after having codes cleared just a few hours ago. I've spent so much money and getting nowhere. Car is 08 Hyundai Elantra GT 144k miles. Maintenance is always routine and up to date. Any ideas would really be appreciated. Ty in advance.

 

Something like this is impossible to diagnose over the net.. It will require a thorough check of the entire exhaust system and under the vehicle to see where the fumes are escaping and getting in. Where you take your vehicle for repair has a lot to do with finding and correcting the problem.
A muffler repair shop could probably find and correct the problem, but you may wind up buying an entire exhaust system which can be a little expensive, and it will be worth the cost. Get some estimates.