Weird Problem that is hard to diagnose.
 

Car: 1990 Miata 1.6, 5-speed, M45 Jackson Racing SC. Afpr, Msd boost retard.


If it is hot outside my brothers car starts well. If it is under 90 degrees it doesn't start. It will start and die. start and fail. But as soon as it fires enough to get it to roll, it instantly runs.
It acts like a fuel pump halfway working. It hits to fire up fast and dies.
When it is hot, it fires and runs great.

I told my brother to put our spare O2 sensor in. He never did.
But he has replaced:
Factory fuel pressure riser (spare part in garage)
Fuel pump (new)
Fuel filter,
Pcv valve,
Plugs,

It seems kinda like the choke isn't working. And it is progressively getting worse.
Now it is starting to cut out on the highway. Normal driving and the narrowband goes to lean and it stalls and then kicks back in.

I need to find out which relay is for fuel, and we may swap in my old AFM tommorrow.

Will a bad AFM do this? ANY Ideals????

Yea that;s helpful :slap:

But it does sound like a fueling issue, although if you got a spare AFM laying around couldnt hurt to try it.

Thats what I was thinking. I know that 1 or 7 pin goes to the ST Fuse. Which all ties into the fuel pump power. So I wounder if the AFM is jacking with the power signal to the fuel pump.

Try jumping FP and Ground in the diagnositc box. If it runs OK there, the AFM is interrupting the FP circuit.

Thanks.

doesnt that supercharger kit come with a "electrickery" goodie to actually fool th ecu into thinking ambient temps are lower so that more fuel is added ?
my bet is on that box

I have heard something about that. I couldn't find it, I even pulled the kick panel and the stock ecu was there. But it did have blue wiring??? The car has a afpr, and the msd box. Would it still have the black box?

Where would it be.

Thanks!

Would you happen to have a schematic of the box? Thanks.

Someone else may have it handy, or another Miata in your neighborhood should have it inside the cover.