RWatters

iTrader: (5)

When I picked up my RX-8 I noticed it had a random and intermittent miss at idle. Every probably 5-10 seconds or so it'd have one little sputter but otherwise it'd idle normally. When I say sputter I mean it's a miss you can hear in the exhaust but otherwise wouldn't know it's there. It does not try to kill the car, the idle does not fluctuate RPM-wise, etc. The idle feels a little rough (you can feel vibrations inside the car when it's idling) but I figure that's because the motor mounts are the original and it's a 2004 (2003 build date). Idle speed is around 800-850rpm.

1-2 months ago I replaced the coils and spark plugs in my RX-8. The plugs looked like the originals and were in pretty bad shape and two of the coils had some slight heat damage on the outside of them. They were also the originals. So much for the TSB for inspecting and replacing them!

Once swapped out the car ran insanely smooth up until about one week ago and that same intermittent sputter at idle is back. It revs perfectly fine, it gets 18-19mpg (city/highway mixed driving), and it pulls throughout the RPMs like a healthy RX-8 should.

Is this little miss or sputter normal or is it indication of something I should start to worry about? The car is an '04 RX-8 with 31,000 miles on it. Oil was changed 1,000 miles ago, plugs/coils changed 500 miles ago. It's the original motor and sees redline at least once every time I drive it. I have not done a de-carb procedure (and frankly I'm a little worried to since it's an original motor with little to no oil-change history per Mazda NA).

Edit: I checked the plugs over the weekend to make sure they hadn't backed out and were still good. Leading and trailings were installed in the correct spots as well (in case someone wanted to ask that). I'm going to check the coils tonight to make sure the connects are still tight on them.

TIA.

@!!narotordo

Hook a timming gun up to the spark plug wires to see if the light is constant. If not you need to replace that coil. Check each one. Mine where always going out till I got a ignition upgrade.