rough idle car seems to want to stall
 

Hi everyone, as you can tell by the title my car idle's pretty rough lately and seems like it wants to stall. Sorry if this is long but I'm going to try and get most of the info out there at once. It's an 05 AT 4spd 62K miles daily driver run hard every day all the recall work done and latest flash(except I thought I read about a new one maybe in the past few weeks maybe??). This just started about a week ago when it started getting pretty hot here, over 100 every day now. Yesterday my car thermometer was at 112 when I went home from work. The rpm's will fall at idle to the 750 mark and the car gets shaky and seems like it's sputtering too, it's dropped below 750 a few times and then it REALLY feels like it's about to stall but never does. It also will happen on startup. There's a slight hesitation to it now seems like but it only lasts fractions of a second but you can tell it's there. I've had the spark plugs replaced within the last 20K miles for sure but I don't know exactly how long ago off hand. I'm kind of questioning my exhaust system....it's stock but at least 6 months ago or so I went over to my dad's and I was parking and was revving it up a little before shutting it off, nothing excessive probably no more than 4-5krpm and heard 4 loud backfire pops as the rpm came down to idle from the exhaust. I had NEVER heard my stock exhaust pop like that, it was so loud it sounded like someone was beating on the trunk of the car and since then I can make it pop on command once it's warmmed up. Just a slight blip of the throttle to rev up to only 1500 rpm no more than 2000 and it pretty much pops on command. I know it's normal for rotary to backfire but I thought the stock exhaust pretty much cut that out this is very audible so I'm wondering if something is wrong there. I'm going to get a new air filter tomorrow if I can just to see if that does anything but it doesn't seem that bad. Could it be ignition coils? Spark plug wires? Maybe a cat failure? I was looking at getting the mazdaspeed exhaust, intake, and rp supercat at the beginning of the new year but I couldn't afford it right now. Even after the loud pops I heard at my dad's a while back I've never had any issues until now. Any suggestions are greatly appreciated.

JT, you're on the right track with your thoughts on the ignition system, especially with the mileage you have. There may also be a vacuum leak somewhere. Start by looking around under the hood for any loose vacuum lines or intake duct clamps and MAF mount screws. Do you know how to use a vacuum gauge? This'll get you started. I wanna try and make some progress without having to spend money on swapping parts.

I don't know how to use a vacuum gauge or what that even is? I'll try and search up on it though. Thanks!

I too have the same problem, with out the back fire part.
It have been 100+ in memphis for the last week. Well when I take my car for a long ride (35-45 mins) with the AC on. When I get to a light from the interstate. My car will start to shake as if it's going to stall. One time it did. I would not start after that. I then let it sit for about two min. then try to start it again. This time it start.
I've been doing some reading and finds out that our car have heat problem some as instructed I've taken off the rubber pieces by the front winshiel.
The car never dies on me again. But it will idle really bad when it hot and I have the AC on. Oh..... It's an 04 MT with about 38k

JT, do you have any interest in learning about and working on your RX-8? If so, I'll guide you on which tools to buy as problems comeup or you decide to do your own mods. If you are interested in learning then you'll want to get a manual vacuum pump from an auto parts store.

Oh I totally want to learn everything I can, I wish I could do my own mods too I just don't have the knowledge or toolset to do it or even the courage without an expert standing next to me, too afraid I'll break something. I've already done suspension and brake upgrades i wish I could've learned how to do those. Definitely want to do the intake and exhaust myself because those can't be that hard. I'll check the local auto stores and see what I can find on getting one of these gauges.

The reason I am suggesting you get a manual vacuum pump is that you can use it as a gauge and still use it later as a diagnostic tool for S-DAIS diaphragms and a manual brake-bleeder/clutch bleeder pump, too.

I'll be in Dallas/Ft. Worth on Sept. 11th or 12th if you wanna hang out with a TX crew while I install a nitrous kit and maybe some other stuff, too.

Oh that would be totally awesome!:rock: Definitely!

Keep an eye open as I am about to post on the Gulf Region sub-forum. I have one guy booked already.