This is a VW Jetta made in 1984 with 1.6L petrol engine (code "EZ"). It starts OK (though if it has been a wile since last start, it takes some cranking to start the engine), but when climbing a hill, the engine starts misfiring and obviously loses power, so much so that if the hill is steep enough it looks like the car may not be a able to make it to the top. When idling (the automatic transmission in "P" or "N" position), then engine still misfires, but rarely (like once every 10 seconds).
Another weird thing is that if the transmission is in "P" or "N" position, the idling speed is ~1500RPM, but if I put it in "D" and apply the brakes, the idle speed drops to ~900RPM (this is what the manual specifies).
Previously the car had problem starting, but I found the reason - bad capacitor and, in turn, worn out contact breaker points. I replaced the points and the cap (didn't the a proper one, so just used a regular 630V 0.2uF capacitor). The spark plugs are new.
I checked for vacuum leaks, found one (the air intake vacuum unit is broken) plugged it (temporarily just plugged the tube), but that made no difference.