I have a 1980 Rx7, 12A GS. Ever since I have taken off the smog pump and put in an exhaust header and straight pipe exhaust, the engine runs rough at about 2200-3000 rpm. It purrs smooth at idle, and runs fine when I rev it up past 3200 rpm. My thoughts are that I need a fuel pressure regulator and/or a bigger fuel pump because it may be leaning out. It also likes to backfire sometimes between shifts as well. A regulator will probably help that problem as well. I had the timing checked out, and it was fine, and the idle speed adjusted. But it still likes to buck and sputter at that rpm range. I want to get this fixed, but not sure what specifically would take care of it. Any one know or have any suggestions? Please reply or PM me - Thanks.

 

How old is the coil?

 

the coil is stock....so 26 years old!

 

I've encountered that problem once before, and it ended up being my coil.... They cost, what.... 20 bucks? I'd give that a shot first.....

Dan

 

Did you go to a different carb when you did the header ?

If not maybe the vacuum advance is messng with you until the mechanical advance kicks in @3 - 4000 rpm. I'd try disconnecting the vacuum advance and see if it makes a difference. Your idle may suffer though.

Also check for vacuum leaks since you removed the smog pump that implies you had to mess with the rats nest a bit as well, right.

I wouldn't run out start replacing parts yet, I would start first by making sure what you changed isn't the cause. It could be a real simple fix if its a vac leak or something like that.

 

the backfire is do to the fact that the exhaust manifold you removed had a check valve in it and the header does'nt. I would buy an A/F ratio meter and check out what you are running. Summit sells a good one for cheap from MSD ignition that comes with a sensor. Also British sells one to check each chamber that screws into the engine where the spark plug goes. Then adjust the carb as needed. Go here if you can't figure out how to adjust the carb: http://www.wankel.net/~krwright/cars/rx7/manuals.html