I'm having an interesting problem with my 1991 RX-7 N/A Coupe - auto transmission.

Engine power seems to be good in the 1-3 gears. It comes off the line like a bat out of hell in Drive, S, L. But when I get up to about 65 m.ph. there's no reserve power left. You wouldn't notice a thing wrong with it in city driving but when I'm on the freeway at 65 mph and going up a hill, it just won't keep up.

If I floor the engine standing still, it seems to have plenty of power, revs sweet at the way to red line. The transmission seems to shift gears smoothly right into fourth, as well. It's just when it gets into fourth, I can hold speed around 60 but it really takes some time to get up 65 and above.

Any ideas?

 

Maybe your 5th and 6th ports are stuck. Check the archive for how to fix it or do a search on auxillery ports. Your cats may also be clogged. Do you have lack of power around 3.5k-4k rpm?

The revving at idle seems like a reasonable explanation for the ports sticking since they only open under load.

 

Check you ignition system, spark plugs, wires, etc....

 

Well Check compression.

But it sounds like your 5/6th ports aren't opening.

My car wouldn't go past 100mph with them not working.

The easy fix would be to push them with your hand to make sure they move. Sometimes they will be easy to move or semi stiff. Put some lithium grease on the rods and the push it in and out to work the grease in.
Wipte the excess off the rod so you don't collect dirt and give it a drive. Hopefully it fixed it.

 

Oh yeah, The obvious stuff too.

Make sure the spark plugs aren't fowled and that trailing and leading are in right.(I've done it before.DOH)
That kinda gives a bad idle though.