I have a 91 honda civic. Running with new plugs,wires dist.cap & rotor.At idle I remove #1 plug wire with no change in idle. Remove any of other 3 and deceleration. What's wrong?

There is a problem with the number one cylinder....either ignition wise, or mechanical wise.

Have you done a compression test on all 4 cylinders?

Did it do this before you replaced the plugs, wires, and cap?

Ensure that the #1 spark plug wire is fully seated in the distributor cap--it's best to apply dielectric grease to all connections. I'd also check the spark on the #1 cylinder. If its okay, you may have a valve or fuel injector problem.