I just recently purchased an '85 Rx7 with the 12A engine. I don't know anything about how the carb is supposed to work on these beasts so hopefully some experts here can point me in the right direction.
First...the engine runs great and smooth at idle. However, it runs rough all the way up thru the gears, and at highway speeds chugs along...I would almost compare it to a 'miss' in a conventional engine. Flooring it thru along the gears causes the engine to run smooth and powerful, but unless you are really driving it hard, it just 'burbles', as I call it. So basically it runs like crap. The guy I bought it from said he figures it has something to do with the the carb not making a smooth transition between stages. There is a vacuum line disconnected at the present time, which is sealed on the end.
I have the car booked to go in to the local shop on Tuesday. I'm looking for ideas on what to tell these guys to look for. Any ideas appreciated.

 

the carb probably just need a rebuild.

 

Fuel filter could be part of the problem too.

 

Change fuel filter- absolutely.
Try new plugs and check timing, too. Get a Haynes manual and a non-dial type straight forward timing light.
More than likely you have a crappy filter. Yo go zoom-zoom through the gears because the accelerator pump is squirting fuel in for you, but if you can't cruise smoothly at 5K rpm or more, then it's a filter thang.

 

OK Thanks...I will change the filter and try it...any ideas why one of the lines are off with a plug in the end of it?

 

Which line? Take a pic if you can...