If I don't drive my 04 Rx-8 for a couple weeks in cooler weather (which isn't that cold, more like not warm), when I first start it it idles rough and the check engine light flashes a few times (misfire indication) for 10-15 seconds. It will only do this when the car sits for 10-14 days without being started. After 10-15 seconds the idle smooths out and the flashing stops and it runs normally and makes good power. The car has cat and aftermarket BHR coils (that should still have lots of life left in them) and has decent compression (checked with rotary tester). Any thoughts on what to check?

 

Is there a sweet smell from the exhaust or is your coolant going down slowly? What could be happening is a slow leak of coolant into the chambers. While the car sits enough accumulates to cause problems until it is burned off.

You can also pull the spark plugs to see if there are coolant deposits on them.

 

Left my car sitting in garage for over a week. Started her up last night and stalled out twice before getting CYL 1 and 2 misfire code.







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get a coolant pressure test done