Are cars harder to start after replacing the sparkplugs ?

Answer this at bunny.sprks@gmail.com

If your friend got all of the broken plug out there should be no problem. The plug wires might be crossed,check firing order to confirm placement of wires.

If he forced it out he could have warped the alluminum head and might have excess O2 getting in.

Yea, that would be a good reason.

the spark plug is what ignites the gas to start the car. if you can't ignite the gas as easily, it will be harder to start.

No the car should be easier to start. With all new ignition components it will have better spark. If he did not relace plug wires and cap and if vehicle equipped with. when The old plug wires are removed to install the pluds they sometimes break inside where it cant be seen. Always do full tuneup. If only 1 part is replaced the other old ones can kill the new ones. A wire might just be crossed or not on all the way also. IT could be a bad spark plug if dropped 1 time a plug could be ruined with even without seeing any damage. Can also change fuel and air filter will be beneficial esp. if car is computerized. now car will burn fuel at better rate and change emission readings into computer and make hard to start if something in system is bad.