I just bought a 91 RX7 Convertible, with a motor with 25,000 miles on it. It drove fine, I think , I didn't notice any prblems, then I put 89 Octane gas in it and after about 10 - 15 miles it is hesitating throughout the powerband. Can there be anyother cause to this? ( I haven't seen any complaints on any 2nd gen cars, just the 3rd gen) Also, My check engine light is on all the time, except when foot is on gas. What can these problems be? Any help determining the problem is appreciated.

 

Stock non turbos will run better on 87 octane, but that should not effect operation, you'll just be down a little on HP.

You will need to pull the codes from the ECU to see what the problem is.

 

did you tigten the gas cap.... i dunno if our cars do this (never tried), but on my dads honda if you didnt tighten the gas cap to 3 clicks it would throw a cel and not run right