Nissan Repair: 00 Sentra Engine problem, rubber boot, new spark

Question
hi i own a 2000 sentra and a couple of months a go my engine started to shake and vibrate really bad. so i took it to a shop to fix it they said that on of the rubber boot for the spark plug was bad so they replaced it for which cost $80 for the rubber boot. It was running okay after a few days after they fixed it but started to shake and viberate really bad again. I already replaced new spark plugs and im pretty sure they re in the correct slots. Also when i stop at a light the car shake twice as much and make a lot of noise from the engine. But some time (rarely) it becomes normal without the shaking or viberating or noise from the engine. would you have any idea what is causing this problem.

Answer
Thiri,

The one rubber boot that was replaced was probably the part that goes into the head to connect to the sparkplug.  The shop does not want to take advantage of you so they replaced only what was defective.  So, one boot was replaced and now it looks like another is going bad.  I would probably replace the three that were not replaced the first time and just be done with it.