I guess #4 cyclinder misfiring?

For check i removed all plug wires one by one. When it came to no.4 idle didn't change.

After this, i replaced rotor arm, plugs, wires, cap but still does same thing.

i can see spark from cable to cap but with no idle changes @4

what can be the problem?

2.0 Ford pinto engine with weber 32/36

If you have spark on number 4, run a compression test. Perhaps you have a burned valve.

Did you tested cables for ohm resistance?
If the #4cable test way off, that is the problem. Did you changed the #4 spark plug to another position say like 3 or 2 or 1? Did the misfire changed from 4 to the new location of the SP, then its the SP,
did the old sp came out full of carbon deposit or melted, maybe the center electrode was chipped as in missing a bit of the ceramic? If the car passes these suggestion then chances are the the head needs to come out. The compression test AND/ leak down test will show no compression at #4.

also are you missing a rag by any chance? Make sure there's nothing blocking the #4 intake manifold runner. I've seen rags lodge in there and noone knew about it, until the I.M came off.

almost forgot. Inspect rocker arms as well. My brothers minvan had a valve lifter colapsed and the valve was not opening even a compression test would had shown a zero compression (it was the admission valve rocker arm lifter that broke)

make sure that webber is putting out enough fuel from the ventury closest to # 4, it might be that that side is clogged and not enough fuel is reaching #4.
BTW new doesn't mean good, they can be deffectvie

Check for compression

Bad fuel injector or wiring to the injector, Possible bad driver in the PCM. Bad compression.

Do a compression test. If that ones low you've burnt a valve.

The cylinder not working could be for several reasons.

Check the compression of All the cylinders. Report your findings back to us here.

Since you'll be taking all 4 spark plugs out, how does cylinder #4 spark plug look, compared to the others? The same, or different? Oily? Carbon fouled? Wet from gasoline?

The old way looking for cylinder problems, involved using a vacuum gauge connected to the intake manifold, and pulling spark plug wires one by one and watching how far the vacuum dropped. It's a more sensitive method than listening to idle or watching a tachometer.

I checked resistance of cables and plugs all good.

is it possible spark plug not grounded well so it won't spark.

how i can test ground?