What causes misfires?
 

What is the cause of a misfire?

I had one and my brother had to replace a cyliner.

What could it be? Very fast accelaration?

RE: What causes misfires?
 

plugs, wires, ignition timing?

RE: What causes misfires?
 

injector could be totaly clogged, that would cause a misfire...which is when a cylinder doesnt complete its job. So a totally blocked off injector could be minimizing the fuel goin into it and not getting enough gas to combust fully. Find a VAGcom or take it to a dealer, it will tell you if it is a misfire and which cylinder (if u dont kno it is a misfire for sure)

EDIT: i worked on a f150 at my shop with a misfire in cyl 5. could be all of the things sandman said plus injectors. Like we replaced the wire on it, still missfired, then replaced the injector and it worked. plugwire, plug, or injector is ur best bet.

RE: What causes misfires?
 

What about throttle body issues? Couldn't that also cause a misfire?

RE: What causes misfires?
 

anything that would cause an incomplete combustion can lead to missfires. anything to do with air, fuel, and spark.

RE: What causes misfires?
 

Cracked, leaking intake mainfold, could have a leak at the TB - intake connection. Bad coilpacks, plugs, dirty injectors, the list can go on.

RE: What causes misfires?
 

couldnt he put in a few bottles of fuel system cleaner, like gumout regane or lucas oil cleaner.