Golf 93 GL 1.8 with failure

Could someone help me?
My Golf stalls when downshifting (when braking at a traffic light). It runs fine at higher speeds, except that it jerks a little when the fuel is low. I changed the spark plugs and they came out black, I changed the fuel and air filters, and I added fuel injector cleaner to the tank.
I suspect it could be a sensor, since I disconnected and reconnected one located on the opposite side from the throttle cable, and the problem was fixed for about 15 days.


Thanks in advance

Does it stall completely?

I mean, just like that.

Or does it go "tatata, tatata, tatata..." and then gradually decrease until it stops?

This is crucial to know if it's an ignition problem or an idle control issue.

Does it always do this?

Or only when it's cold, or only when it's warm?

Try to be a little more specific so I can tell you what I mean.

I agree with Traller, try to be a bit more specific.

The "throttle cable" thing??? I have no idea, I don't know what you mean.

Anyway, if the spark plugs are black even though they're the correct ones for the engine, it indicates two things:

1) You're burning oil

. 2) The fuel mixture is too rich.

The difference between the first and second is that when you burn oil, there are deposits and scum. And in the second case, it's fine, black soot, like dust.

The correct color should be gray or yellowish-brown on the lower part of the insulator next to the center electrode.

Regarding the symptoms you mentioned, I suppose the fuel injection is more likely to be the problem than the ignition.

And assuming this only happens when the engine is hot, it could be the throttle position sensor, the idle air control valve, the engine temperature sensor, the mass airflow sensor, and a hundred thousand other things, so please be a bit more specific.