Dealership Can't fix my problem :-(
 

OK, I took my 2004 rx8 (100,000 miles) to the local mazda dealership. I had them install race headers, catless pipe, and full catback exhaust. I also had them install an ACT streetlite flywheel. While it was in the shop they replaced the starter as well. Here's the problem, car starts fine, idles at 1,000-2,000RPM's upon start for the first minute, then idles at 500RPM's. After about 5 mintues of driving, everytime you stop the car the engine dies. Starts back up just fine though. The dealership told me that the flywheel I ordered (13lbs.) is way to light for my engine and that is why the engine dies at every stop...This is a huge annoyance and I do not believe that this could be the problem, I've called 3 renowned Mazda tuning shops and they all said the flywheel being the problem is impossible. I also called 3 other import tuning shops and they said the exact same thing. I even called ACT and they said, their flywheel can't be the problem of the engine dying. Could somebody please help me out with this?

I'd check for vac leaks.

It's not the flywheel, that's for certain. Frankly I'd question the competence and reputability of the Mazda dealership you brought it to. Based on your post, I see several red flags that lead me to think these guys are shady. First, why did they replace your starter - was it broken or causing problems? No need to do so given the job described. Second, by doing the full job described (i.e., presumably by chucking your cat(s) to replace with headers & catless pipe) they intentionally run afoul of federal laws against tampering with emissions gear, irrelevant if you ordered them to do the work or not. Reputable dealerships generally don't do this sort of thing, even on a car that's got 100K miles or is out of warranty.

Back to your question, I'd start looking for any & all electrical connections or vacuum hoses that may have been distrurbed during the course of the work. My guess is you'll find something they forgot to reconnect or may have broken. I'm not too familiar with the RX8, but the work done requires removal of LOTS of components to do the job. Does your check engine light (CEL) come on, or did you try reading the CEL codes using an OBD-II code scanner in case the CEL isn't on, but codes may be stored?

He probably had the original, recalled weak ass starter. I would (and did to mine ) upgrade to the new one. Makes the car start immediately.

And yes, it sounds like it has a vacuum leak or something. However, if that was the case, you should have a light on. If you don't, I would still hook it up to a scanner that can read real-time data from the ECM.

When was the last time (if ever) you cleaned the throttle body?

They get pretty gunked up form the PCV system. I know mine ran a shitload smoother once I took mine off and cleaned it.

Interesting, had no idea they recalled the starter. Is that something Mazda replaces for free under warranty, or is this recall optional? Good to know info regardless, incase I ever pick up an RX8.

Did they replace the counter weight when they replaced the flywheel with a light weight one?

I would think that it would be VERY obvious if they did not put on a counter weight. If I remember correctly, the counterweight is actually a part of the stock flywheel, so if they just put on a flywheel and no new weight at all the engine would prolly run like crap.
Definitely sounds like a vac leak, or something not plugged in right. Start at the front of your engine bay and check every connector to be sure they are connected correctly and completely. Then follow every vacuum line, making sure they are connected at both ends.

I've had a similar problem with my '04 RX8 twice. But it was caused by 2 different issues.

The first time, I installed a new midpipe. It messed with the readings from the O2 sensor near the catalytic converter. That in turn screwed with my fuel mixture, causing the engine to stall when the RPMs slowed to much. It also idled very rough, and would almost stall while idling. If that does turn out to be an issue for you, it helps to reset the ECU setting to factory. It will help until the computer starts to change the mixture again.

The second time, the car started dying for no apparent reason when I would stop, and I would occasionally notice a flicker in the radio display. After much trial and error, I figured out that I wasn't getting an even flow of power from the battery. My contacts were clean, but not conducting properly. I replaced them with a $5 set of contacts from AutoZone and haven't had an issue since. Since we both have an '04, I suppose it could be worth checking.

It sounds like the first step would be a reset of the ECU. The light flywheel and exhaust changes will affect the fuel mixtures at idle or when coming in/out of gear. Disconnect the battery and let it reset completely, then reconnect and drive around some going through the gears.

I agree that it "sounds" like a vac problem, but none of the work you had done should have touched any vac lines. Just sounds like it hasn't learned the changes yet and can't hold the idle when the RPM falls too low.

You should have a CEL by now too for sure... I'd run the codes on 'em all...

You can also do this to reset the ECU (this is how I used to do it):

1. Turn ignition switch to ON position, but do not start engine.

2. Quickly pump the brake pedal 20 times

I dont own an Rx8 but... isnt this pretty low idle for rotary in general?:dunno:

I know i dont like my idle on my FC that low.. I think i had mine set somewhere between 750-1k rpms.

My RX8 idles at approx 850rpm (with a bit of hunting) according to my data logs.
The ECU reset thing is probably a good place to start, but it could be a lot of things. The main reason I say reset the ECU is, purely coincidentally, somebody in a thread on AccessPort tuning I was reading yesterday commented that their car died and had a hard time idling due to having issues with the learning the fuel trim on their new map.

Speaking of ECUs, being an 04, what flash version is the ECU on? The 04 RX8s got more updates than Microsoft Windows for the first year or two.

As for the starter, the 04s (and I think some 05s) had a hard start TSB with one of the fixes being to exchange for the updated starter which is much better. It wasn't a recall, but if you were still under warranty and complained about a hard start, most dealerships would just do the swap, especially if you pointed them to the TSB.

+1

this is my thought as well.

on a totally separate note, i'm impressed that you found a Mazda dealer willing to do all that they did to your car.

it wasn't a recall, but they do have a bulletin that says to replace the starter if the car has the symptoms (off the top it might be flooding, but i'm not sure). there is also a bigger battery.

the starter takes cranking rpm from 225-250 to like 350, it makes a big difference

They plug the WBO2 sensor back in?

Transmission switches can cause strange idles......check those connections as well

Both of theose would have been disconnected to remove the tranny