zoom44

thermostat too! if its not operating correctly it could lead to reduction in fuel mileage

WTBRotary!

iTrader: (6)

Check CAT, I really think thats what it could be. Ive been through a couple of CATs to know what they do when they go bad...

GeorgeH

iTrader: (2)

^When mine went bad I had serious power loss. The OP has said the car doesn't have obvious power loss. When yours went bad, did you not have high-rpm power loss?

ASH8

142K and ONLY on your third set of Spark Plugs!....WOW...

I would hate to think what the GAP is on Plugs that OLD....WOW

Congrats being on Original Engine..

Grace_Excel

iTrader: (5)

I'm the second owner, original engine, and dealer maintained until I bought my RX-8 at 108,000 miles. Besides the 3-5k mile oil changes, the battery, the radiator, and the clutch; I didn't change my spark plugs until 142,000 and the coils until 148,000. I'd have to dig in and look at the original owner's receipts of what changes and maintenance were performed before mine.. I've experienced various CEL, the lag in power, and low mileage which led me to change the plugs last October and the coils last December; still running with original plug wires.

I've never really had a real serious problem, flashing CELs were pretty common before the plugs were replaced, I had a case of dirty MAF once when I overflowed with topping the oil of which I thought was caused by premixing with TC-W3 at 143,000 miles.