The car is 1993 Volkswagen Vento(Jetta III), with 2.0 8v (2E) engine.
The problem is, that some time ago, the idle went a bit rough, at first it didn't bother me much, but then it got worse, and now today it started to jerk a bit even when accelerating.
When idling, occasionally the rpm drops down to like 350 rpm for a sec, and at other times just keeps jumping up and down between like 600-700 rpm really fast.
The problem occurs both when the engine is cold and when it's warm.
It did appear before, that there was some sort of loss of power, when the engine got to working temperature, but now, it seems kinda "weaker" all the time.
I've replaced the distributor cap, distributor rotor, temperature sensor, air filter, vacum hoses, and spark plugs, but the problem just seems to get worse every day. The old spark plugs seemed to be of very strange color also.
Anyone got any ideas what to do/check?
Picture of old spark plugs:
Modified by Mr47 at 2:32 AM 6-25-2009