Hi there, I've made some researches but i found nothing, so that's the problem.
I have a 1985 all stock gsl-se (13b) with about 90k miles on it. Fresh spark plugs, wires, distributor etc... with 6-8oz of 2-stroke oil in every tank of gas. The problem is, sometimes (not always) when i start the car cold, the idle isn't going to the +/- 2000rpm by itself like it used to (and i think should) do and it idles quite rough at about 4-500rpm until i just press a bit the gas pedal (sometimes one kick, sometimes it needs a couple), than everything seems to be good and the engine is revving at the said 2000rpm for a couple of minutes, than drops to normal 850rpm. Occasionally again, the engine is going to reach 2000rpm when i "coldstart" it, but will quickly drops to very low rpm and completely shut off after a few seconds if i don't press on the gas pedal. Any suggestion on how i can solve this problem is welcome and appreciate, thanks.

ps:It's my first post in this forum so i hope i'm in the right section and also that i explained well enough

 

Hey, welcome aboard!

The thing about the -SE start cycle is that the fast idle cam must be manually set by the driver before turning the key. That means, get in, push the gas pedal all the way to the floor ONCE, and then release it, then turn the key to start.

What this does is rotate the throttle body rods to the Wide Open Throttle position which sets the fast idle cam. As the engine warms up, hot coolant from the radiator flows to the Thermowax Pellet, causing the wax to melt and releasing spring tension, allowing the throttle RPM at idle to gradually return to the factory 800-900 RPM. This occurs slowly over time as the engine heats up with the intention of running slightly rich and fast to heat up the catalytic converter for best efficiency.

In fact many of the fast idle cams were positioned to bump the col start throttle position to about 3k RPM which is pretty high for a cold engine. Regardless, the Mazda designed system works well when you follow the start procedure i mention above. Good luck,

 

This^^ Though have to add,all i've ever done with mine since i've owned it is to lightly depress gas pedal,can hear and feel the click of fast idle cam engaging. Has never failed to start and run at approx 2200 rpm til gradually lowering idle speed as it warms. You could drive away with the high idle speed,but always let it warm enough to drop to base idle,temp. gauge moving off cold before driving away. One of the most reliable cold starting cars i ever owned. Maybe a good throttle body cleaning would restore proper cold start performance for op.

 

Thanks for the information, i didn't even know about the fast idle cam. I've tried this morning and it worked good so i hope it was the issue.