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 answers asap.
If the apex seals go it does not burn oil, only if the oil seals on the side of the rotor go bad. Pull the plug wires off and crank the engine. If the compression is even (the chugging at even intervals) the apex seals are ok. If you get a chug, chug, chug, then it seems to spin freely before back to the chug, chug, you may have blown an apex, side or corner seal.
Alternate. Pull both plug wires off either the front or rear housing. Try to start it. It will run on one housing, just not well. If you have blown seals, it probably will not start on one housing.
my best guess something happened to a spark plug