I have a 2007 Mazda 3 with a 2.0 engine and automatic trans and has roughly 75k miles. When the car is in drive, it has a super rough idle. Idles at about 500rpm and bounces between 500-600rpm only when in drive though. When I put it in neutral, it stops and has a smooth idle at 750rpm. But as soon as I put it in drive, it drops to 500rpm with a rough idle. No check engine light is on nor is any other kind of light. Anybody know what is going on?! Im mechanically inclined but am stumped on this one Anybody?!

 

Not an expert by any means, but I have read that it is common for the EGR valve to get clogged. It could be that it is the problem. You can try taking it off and cleaning it with some carb cleaner. Make sure to get a gasket though since most likely you'll mess up the one that's on it when you remove the EGR. Hope this helps...

 

thanks man. i'll try it. i also saw a service bulletin that said the throttle body builds up with carbon causing less air flow causing it to idle rough and sometimes stall.

 

the throttle body getting dirty could definitely do it - search the forum though, I know i've seen this sort of problem posted before.