Today I was driving my RX-7. When I stopped at an intersection. The car was running fine. Then as I pulled out, I heard a very loud backfire. The RPMs were around 4k but were jumping to 5k and then back down randomly. It continuously backfired as I limped it home. Although it was reading 4-5k rpms, it didn't sound as though it was revving over 2000. Bad misfires, loss of power.. I checked the spark plugs, which were all firing correctly, checked the vacuum lines, and it's getting fuel, but won't run unless you hold the pedal down a little when you start it. As soon as you let off, it chugs down and dies. No excess smoke, so the apex seals are still intact. Engine was rebuilt 70k miles ago, oil was changed 200 miles ago, as with the gear oil in the transmission. I have no idea what could be wrong. I need some answers ASAP.

 

A busted apex seal won't generate smoke, unless you also busted a coolant or oil seal. It couldn't hurt to do a compression test.