I just recently bought a 2005 Mazda Rx-8 Sport Automatic with 72k miles on it, roughly 2 weeks ago or so. About a week ago my check engine light came on and had it tested. The issue was misfiring so I decided to buy new spark plugs and wires. Just last night I replaced my spark plug and wires, as well disconnected my battery for awhile. Once the process was done and over with I fired up my engine and let it ran for a good 10 minutes before driving away. However once i started to drive away everything seemed to be running beautifully until I came up to a stop light and my engine idled and died (First time happening in this car). I eventually had to get towed back to my original destination, and once we looked over it all once more, but we couldn't find a issue. My car did fire up and ran just fine in the garage, so being a dare devil I tried to drive it once more. Only got about a mile away before the same issue happened. Any help?

 

One big question: Why did you have it towed? Did it not re-start? You only mention that it stalled.


The most likely scenarios:

1) Disconnecting the battery clears the fuel trims. Letting it idle for 10 minutes should have stabilized the idle fuel trims enough to keep it from dying, so you probably have something else going on that disrupts the fuel trims at idle, like a vacuum leak.

2) You replaced plugs and wires but not coils. Coils are very important, and need replacing every 20k-30k if you use OEM coils. If those are dying, new plugs and wires aren't very useful since there isn't a very good charge going through them.

3) You might have low engine compression, which can cause misfires, and can also lead to a stalling engine at idle that has difficulty refiring.

 

I had the car looked at nearly two weeks ago at a mazda dealership. Engine compression was great they said, and yes I had the car towed because it wouldn't start. However when this occurrence happened a second time I just had it towed to my mazda dealership for them to look at it.
Thanks for the information however, and I'll keep all that in mind.

 

If they just told you "compression is great", be very suspcious. It's often an offhand remark by people that never actually test it.

If they gave you 6 test scores and 1 or 2 RPM numbers that the test was performed at and they were properly evaluated and normalized...then you can trust it.


Dying when hot and failing to restart could easily be very bad compression. It could also be a fuel pump failure. HOW it dies is important to know which one to investigate first.

 

You were completely right. Ran a compression test and got the results back today. Resulted in failure to meet the standard in both rotors. Welp...

 

Yeah, unpleasant news. Low compression RX-8s are offloaded to the used car market regularly. Compression test before purchase is something we highly advocate.

 

I was told the same thing by my dealer but they never actually tested it warm. Turned out the engine would get warm and would lose compression and die. Once it cooled down it would fire back up And run ok.