I just bought a 91 non-turbo 13b that wasn't running. After towing it home I found that the reason was the previous owner hadn't done a tune up in a long time. I put new plugs, wires, and air cleaner in it. Got it started and then set the timing. It runs pretty smoothly except it has a slight stumble every few seconds. I notice with my timing light that the spark on the trailing plugs is regular, but on the leading plugs there are fractions of a second when they don't fire which corresponds to the stumbling of the engine. I checked the clearance between the gear and pickup in the crank-angle unit and found it to be 0.010". I also cleaned the two wire leads from the igniter to the coil.

The stumble is still there. Does anyone have a cure or suggestion.

Thanks,
Gary

 

could be the ignighter or the coil

check them both

 

The coil primary resistance is 0.8 ohms which is apparently in spec. I don't know how to check the ignitor. Is that covered in any tech notes?

 

On the chance that the problem could be grounding, I ran a ground link from the battery to the ignitor, but that didn't improve things. I'm still puzzled....
Anyone????

 

There is already a ground from the battery to the engine block. Try changing the leading coil/ignitor assembly. You can find a used one in the For Sale section of this forum for a decent price. Or if you know someone near you who has a rotary engine, maybe you can borrow one from them to see if it solves your problem before you put money on a new part. Other than that, the only thing that I can think of dealing with spark timing is the CAS and the ECU. You can use a multimeter to check resistance on the CAS. Instructions are in the factory service manual, which you can download for free at www.iluvmyrx7.com if you don't already have it. The only other thing I can think of is the ECU. Thats where the signal comes from since its a solid state system.