i had my car's rotor head, distributor cap, spark plug wire set, and spark plugs changed. after changing these parts, i feel that my car get more power when i accelerate. however, i feel that my car make more noise and vibrate when it's at idle. mine is a 93' max. gxe automatic. it's getting very obvious when i step on the brake and in D or R gear. i think that the idle is about 650rpm shown on the panel when i step on the brake and it's in D or R gear. it's really frustrating. get more power but vibrating more after doing a tune-up myself. before getting the tune-up.. my car was really quiet. mine is only 60k miles..and about the change the timing-belt by a dealer tomorrow..

a cylinder aint firing. unplug each spark plug wire on each cylinder. change:its working no change:something isnt right.

Perhaps you didn't gap the spark plugs correctly.

I doubt a cylinder isn't firing, because you noticed an increase in power.

Especially if it wasn't doing it before. I felt really stupid when, after a year, I went to go inspect my plugs and found that the rubber end of the socket I was using the year before had got stuck on one of the plugs. I had been wondering why the plug wire didn't feel like it was going down on the plug! I was lucky, however. The plug appeared to have been firing just fine across the gap thanks to my Jacobs I assume. Worth your time to recheck everything though!

don't most plugs come pregapped these days. I thought all NGK and BOSCH do