Change spark plugs - 2003 Hummer H2

There isnt really a mention on how often you should change your spark plugs some manufacturers say certain plugs are good for upto a certain mileage
Check with your spark plug manufacturers recommendation on spark plug changing intervals

https://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-often-should-i-replace-my-spark-plugs

Why you want change spark plugs wire .THIS IS LAST THING TO CHANGE.Change spark plugs I agree.

Usually when you change the plugs that you also should change the distributor cap and rotor as well. When you changed the plugs with hopefully with the Alero specifications type manufacturer spark plugs that you have to also change the timing belt too is why your idling is low. All spark plugs have a gap in them so your car special plugs should too. You might have the wrong spark plugs with the wrong gap in them so you can ask autozone for the gap specs for your year, make and model plus you can buy the right spark plugs there too. The spark gap will change the timing of car depends on the gap.

CHANGE SPARK PLUGS.YOU NEED SPARK PLUG 3/8 SOCKET.YOU NEED SHORT AND LONG 3/8 EXTENSIONS.YOU NEED SPARK PLUG BOOT PULLER AND A SPARK PLUG GAUGE SET THE SPARK PLUG GAP.NOW CHANGE 1 SPARK PLUG AT A TIME SO YOU MIX THEM UP GET FIRING ORDER MIX UP CAR BACK FIRE WONT CRANK.ALSO CHANGE PLUG WIRES ALSO.

you will need
8mm
10mm
5/8 spark plug socket
3/8 ratchet
3/8 extension (it could be 4in and longer)
and spark plugs factory plugs are pregap iridium
spark plug torque is 13.0 lb.ft
coil torque 8.7 lbf.ft
spark plug part # NGK 1zfr5k-11
# DENSO pkj16dr-m11
and spark plug anti seize on spark plug thread
what you need to do is remove the plastic cover 8mm socket or 10mm sockets
now remove the spark plug covers and remove the spark plug coils too 10mm head bolt you will need a 5/8 spark plug socket and a 3/8 ratchet and a 3/8's extension too
you need OEM spark plugs they work the best
hope this will help

FIRST OF ALL YOU HAVE CHANGE SPARK PLUGS WHEN ENGINE IS COOL.IF YOU CHANGE THEM WHILE ENGINE IS HOT YOU COULD DAMAGE THE ALUMINUM HEADS OR CAUSE DISTORTION.TO CHANGE SPARK PLUGS YOU NEED A SPARK PLUG SOCKET.A TORQUE WRENCH.ITS NOT MANDATORY.BUT IT WILL KEEP YOU FROM OVER TIGHTEN SPARK PLUGS.YOU NEED A 3/8 RATCHET AND EXTENSION.YOU ALSO NEED A SPARK PLUG GAP GAUGE.AND SPARK PLUG BOOT PULLER.YOU ALSO NEED SOME ANTI SEIZE COMPOUND.TO PREVENT DAMAGE THREADS WHEN INSTALLING THE SPARK PLUGS.

In servicing the spark plug . If the owner will be the one to change the spark plug then. the owner should locate the spark plugs . then prepare the equipments that is going to be used to change spark plug .First disconnect the spark plug cable to the spark pug . Then use the equipment to take the spark plug off to the engine. The spark plug should be twisted counter clock wise using the equipment to remove the spark plug.Then replace the spark plug.In returning the spark plug ,using the equipment you have to twist the spark plug clock wise . Then set the distributor shaft turn it according to the proper firing order that will be set to the spark plug if it is 1,3,4,2. Then the distributor shaft mark will be on 1.If 2,3,4,1 then the distributor shaft mark will be on 2. Then connect the spark plug cable , after connecting the owner have to test start the car so that to if it back fires .If it back fires then the owner have to repeat again the setting of the firing order of the spark plug until it will not back fires.If the owner don't have time to do the job in servicing or changing spark plug then the owner have to go to a car mechanic and let them change the spark plug.

You didn't specify whether you have the (4) cylinder or the (6) cylinder engine..... I have a 2004 Hyundai Sonata 2.4L 4 cylinder and I just changed the spark plugs in it. I believe that the 2005 2.4L engine is the same. To locate and change the (4) spark plugs on a 2004 Hyundai 2.4L 4 cylinder engine: Remove the (4) 12mm bolts from the decorative plastic engine cover. Remove plastic cover from engine and place it off to the side out of your way. Standing in front of the car, the (4) spark plugs are located laterally (left to right) in the recessed area underneath where the plastic engine cover was removed. Note: This engine has (2) coils....They are located above spark plugs number (2) and (3) from left to right. Starting with the fist spark plug on the left: Remove the spark plug cable by pulling straight up on the insulated connector. Using a spark plug socket, remove the old spark plug and install a new one in it's place. To access the second spark plug from the left, remove the electrical connector and the spark plug cable wire from coil number (1) and then remove the (2) 12mm bolts that secure the coil to the engine. Spark plug number (2) is located directly under the coil. Lift the coil straight up removing the insulated connector from spark plug number (2). Using a spark plug socket, remove old spark and install a new one in it's place. Repeat same procedures for spark plugs number (3) and (4). Note: If you have the (6) cylinder engine, the front (3) sparks pluge are readilly accessible but in order to access the (3) rear spark plugs, you will have to remove the intake manifold

what is involved in changing spark plugs and which type is recommended?