How often are you supposed to change coil packs? I have a 2004 A4 1.8T with 93,000 miles and had the tune up done I think at 70K but don't know if the coil packs were changed. Engine was running hard so I changed the plugs with NGK iridiums but no change. How do I know if it is 1 or all 4? since they are about $25/ coil pack I would like not to have to buy all at once? please help.

 

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You dont need to change them unless they fail. Or if u just want to upgrade them to the new R (revision) coilpacks.
If ur engine is shaking (misfiring) any time your car is on- than most likely your coilpack(s) is blown + CEL. Otherwise might be a vacuum leak/ bad gap for the spark plugs.
Do u have a CEL?
To find out which coilpack is bad:
car is on, take the first one out, if there is no change than you found it, if your car starts shaking even more- than it is a good coilpack.

 

Sorry for this dumb question, but I have no idea about coil packs. Where is it located and is it easy to change em out for a guy like me that has very little knowledge about the engine and such? Thanks

 

ignition coilpacks located on top of the sparkplugs

 

Thanks for replying AudiProtein. This helps much. My CEL is on. I will check them one by one.

 

always carry a couple in the trunk, you never know when they are gonna blow. Last thing you want is to be stranded on the highway.

 

If your cel is on, but your car drives ok than 99% your coilpacks are ok. Everytime they go out, you car starts misfiring A LOT.