Little background on the car 84 gs 12a 120,000 miles. No ratsnest half torn down niki mech secondarys. Msd 6a rb header accel plug wired ngk plugs. Car runs fine. Will cruise to/from work 20 miles one way 15 pf it highway. Get to a stop light/ decel it will back fire all the way down to 1000 rpm. Normal idles at 800. It will idle rough around 4-500 sometimes stall. Car then has no power. I can pull over turn it off than back on and it will run perfect. Possible ignitor isue? All I can think of. Sorry if this is hard to read sending from my phone. Thanks for any insite

 

Your MSD is your ignitor isn't it?

 

I would check the coasting richer solenoid. What you're describing is the job of the coasting richer system. I would have to do some more research to see how you test it.

The fuel & emissions chapter in the FSM has a few tests fir deceleration you might want to look at. It mentions the throttle position sensor, dash pot, shutter valve and a few other things to check. Good luck

 

On the trailing it is, leading no. Okay thanks for the lead. Shutter valve has been blocked off to hold it open.

 

kinda sounds like the problem i started having but mine's progressively worse....

 

So you have an MSD for the trailing but using the stock ignitors for the leading? Whats your
ignition setup look like?

Anyway, this is very similiar to how my stock SA ignition died a couple of years ago. It drove me
nuts for a week or two. When the car was cold or not hot it worked fine but once it warm up
it would die. Sometimes it would restart after sitting for just a few seconds or minutes. It
progressively got worse over time. Turn out the ignitors and/or the ignition box circuitry was
fried. When I disassembled the ignitor box (remember its an SA) there were some scorched
components.

So your failure could be an ignition issue but it could also be many other things. I would first
make sure your fuel delivery is ok, then move on to make sure the carb is working correctly
and then check the ignition. Bad fuel pumps can do this once they get warm. Your carb may
have an issue as pointed out by clykins.

Its also winter in PA now and I would make sure the choke related components on the carb
work correctly with the mods you have.

 

Im going to start with an ignitor, got a few hanging around. The whole set up worked great for the past few months here daily driving it. This is the only issue Ive had yet.

The ignition is set up like the MSD tutorial on mazdaspeeds? site. Only differences are mines located on the passenger side floor board tucked up and in under the dash. This has really got me stumped because as soon as you turn the car off it will start right away and be 100% again. so i haven't been able to poke around with it acting out.

Thanks for the tips everyone lets see if i can get this figured out tonight.