88 rx7 non turbo ,my replacement used engine , that was rebuilt one time , fires up, spins smoothly but will not run under 1300 rpm, just dies and backfires, cant keep it running enough to get out of cab.
I am using my intake manifold and air chamber from original running engine.

tried changing timing but not solving, does it sound like leaking air at intake?

 

sounds like you have a massive vacuum leak, or a massive dead rotor

 

have you ever seen this engine run or idle?

 

no,havent seen it run before, this engine was bought online from a wrecker 3000 miles away .I am convinced it is good , I started it with front rotor only, and back rotor only , so both rotors are working,
have to find out how throttle body works, which is primary and secondary butterfly valves

 

backfiring on an FC is usually timing wayyyyyyyyyyyyyyyyyyyyyy off, or a blown engine.

you could use the trailing wires for timing, because if you use the leading only for base timing you could have the timing 180 off, since the leading is waste spark it will give the impression sometimes that the timing is correct. funny thing about rotary engines, they will still run with the timing a ways from where it should be.

 

Also silly stuff like is the AFM plugged in? Is the CAS stabbed correctly and not one or more teeth off?

Are you sure that the injectors are working? Failure rate for injectors on RX-7s is staggering after they have sat.

Plug wires connected correctly? Trailings not on leadings and vice versa?

 

thank you all for input ,have to wait for outside temp to rise to around zero c to work on car , had a cold front for a couple of weeks 0f minus 20
feb 9
simpson

 

I feel your pain.....my perfectly healthy truck has refused to idle without a little gas recently.....damn weather. I thing -20 (or in my case -35) just sucks for any vehicle!

i would definitely wait for some warmer weather before doing too much trouble shooting. I can almost guarantee my FB will not start in this cold and it runs perfectly.