My 87 rx7 will randomly start misfiring sometimes it will stop after a few minutes and other times it wont stop. just recently i figured out if i unplug the trailing spark plugs from the coil when the car is running it will ark very weakly a few times then there will be a very strong ark and the misfiring stops this method of stopping the misfiring has worked for the last few months also if i leave the coil disconnected it doesn't ever misfire. What could be wrong? any help would be awesome thanks

 

and I have tried two other coils so I don't think the coil is the problem If you have any idea what might be the problem please let me know

 

Have you checked your spark plug wires?

Rotary >Pistons

 

I have tried different plug wires from another car but i haven't tried brand new ones

 

I talked to this guy with a turbo rx7 and he said it could be the injectors not working properly and that having both coils plugged in would be to much spark for the amount of fuel

 

I guess its possible the injectors aren't firing proper but to effect the spark because of low fuel sounds like a bunch of hooey to me ,but I suppose anything is possible . what kind of ignition do you have ? You can run without trailing . check your leading side and make sure all grounds are GOOD. Check power in your coil power feed ( + ) side wires and make sure they are tight and clean , check your plugs if they are dirty or corroded change them . Same with the plug wires . Check the wire connector at the crank angle sensor and make sure they are all connecting proper ( sometimes the plug pins get pushed back out of the connector and barely make contact . ) Make sure you check all the wires for continuity in case one is broken inside the insulation . Make sure there is nothing stuck on the spur and the pickup sensor in the ( Dare I say it ) dizzy and that there is a bit of a gap (credit card thickness ). One more thing check the power wires going to the coils and make sure they are getting full 12 + volts . That will get you started .Gerald m.

 

I believe it is the stock ignition and i have been driving the car around with the trailing coil disconnected but i will make sure to check the things you suggested. thank you

 

where would i locate the crank angle sensor and i'd also like to let you know that it only runs funny if the trailing coil spark plug wires are plugged in

 

Foxed.ca - Mazda RX-7 Manuals This will give you the FSM's for all mazda rotary cars do a little reading on your car and engine then if you need some help feel free to ask .

Check and make sure the leading wires are on the leading spark plugs and the trailing wires on the trailing spark plugs after you check the FSM's out a bit

 

The plug wires are hooked up correctly and the car runs fine as long as you keep the trailing spark plug wires disconnected

 

I think gerald is probably on track with a wire issue on the crank angle sensor. If it runs fine without the trailing plug its probably off time

 

Have you done any other repairs recently near that CAS or was this out of the blue?

 

its been doing this since the night i bought the car and i haven't had to do anything near the CAS

 

Have you made sure that the trailing coil wires are connected to the right housings as opposed to being mixed up?

 

the plug wires are hooked up correctly. If they were hooked up wrong the misfiring would be constant not random

 

I will try to get a video of it soon

 

I am almost convinced the the trailing plugs are firing before the leading in turn screwing up the compression and fuel mixtures on both rotors . no offense but you seem awful sure of your wiring etc. for someone that doesn't know what a crank angle sensor is . Gerald m.

 

I only said my spark plug wires were hooked up correctly

 

Have you checked the timing? Is the contact between the coil and fender a solid and clean one for the coil must be grounded to the fender adequately to work.

 

Continuity is all well and good for certain applications but wont tell you if only half of the wires are broken or if there is corrosion inside the insulation causing resistance. You need to check resistance if you're looking for weak voltage. Continuity tells you yes or no, nothing in between.

 

I don't remember saying anything about corrosion that is what I was suggesting to check and make sure there was no broken wires . A broken wire more often than not has off and on symptoms If you don't have something constructive then maybe you should keep it to yourself . Gerald m.

 

It was a general statement for future reference. notice how the wires were rulled out already.