TheRealRX8

I recently bought a used Automatic 2005 RX8 with 132,000miles. At first it had issues with it turning over but after upgrading the OEM starter to the new 2kw one as well as changing the battery it started up better but still hesitates a bit. My main issue I've found is that when I an on the highway and try to get past 70mph (or go into 4th gear) the car kinda gives in on me and just drops sometimes down to 40mph and just kinda putters along, any tips or ideas as to what I could do to fix it.

I_got_mail

Sounds like it’s more of an engine issue then transmission related. When was the ignition system replaced? Engine last rebuilt? Fuel pump still good?
Worst case it’s low compression. It’s probably more ignition/ fuel pump related. Could even be a clogged air filter.
damm rotaries are so sensitive.

MincVinyl

Thats pretty high mileage for an original motor. Generally the first sign of low compression would be hot start issues. Potentially the fuel pump is having issues.

When hot does your issue happen at higher rpm? By putter is it like a limp mode for a while then can climb?

I cant speak for any potential auto trans issues.

TheRealRX8

So it has been running pretty good for the most part now after running it with premix and putting a new CAI in it. But for some reason if I don't let it sit for long enough after I start it will limp along at like 10MPH untill I switch to 2nd in manual mode but then shortly after it stops but at some times it has an issue getting over 4rpm and other times I can easily get it past 6. I'm not using it for anything specific just daily driver. It also seams to switch gears WAY more easily in manual then it does in automatic.