There is no real way to answer this question without knowing the firing order, the kind of engine and the manufacture of the engine. I would suggest going to an auto parts store and buying a repair manual such as a Haynes or Chiltons repair manual for your vehicle.
1-8-4-3-6-5-7-2
wrong plugs or maybe the gaps are closed, make sure you didnt mix up wire firing order check for unplugged wires or sensors you may have bumped. did car run before the change?
You probably mixed up the firing order.
By changing them one at a time. If already taken off, check a repair manual for firing order.
yes, its about the timing do one at a time if you are changing them, same for spark plugs too
You don't you can change them while the car is still hot its no problem.
Spark plug tube seals need changing
Obviously- the spark plugs were not the issue :)
You may have the wires to the wrong plugs.
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No each spark plug takes turns at making a spark. If the firing order is 1342 then they spark in that order while 1 is sparking the others are not. The plugs spark when the piston is up on the compression stroke and not all pistons are compressing at the same time. Though this happens very fast, but I still think they are not all sparking at the same time.
That would be very rare.