4th cylinder not firing

[SR_s13]

my car sounds like a go-cart. spark plugs are good as are the coil packs. what to look at next? computer, wiring? whats most likely?

[nismo2491]

do a compression check, make sure the injector is firing.
KEvin

[andrave]

what makes a cyl fire?
1) fire.
2) gas.
Put timing light on that wire. If its sparking and its not firing, then its not getting gas. if it is, then test the wire with a multimeter. you could go ahead and replace the plugs since they are so cheap.
I'm not familiar with the coil on plug enough to diagnose further.

[nismo2491]

you're a little wrong in your things needed to make a cylinder fire in an internal combustion engine. you need
a) compression
b) fuel
c) spark

compression is easy, check that its got compression with a compression tester
fuel consists of gasoline and oxygen (normal air) check fuel filter, air filter (though both of these should affect more than just cyl 4) and that the injector is firing. to do that either use a mechanics stethoscope. or put a screwdriver on it and put your ear against the blunt end of the screwdriver and listen for it clicking.
spark - for coil on plug pull the plug and ground the threads out by holding them on a bolt. keep the plug plugged into the coil. I suggest wearing gloves that are kinda thick for this, shock possibility, now crank the motor or turn it on and look for spark on the plug.
KEvin

[bouncin_180]

injectors !

[andrave]

it would still be firing even if the compression was low... if you think its compression add a cap of oil

[SR_s13]

stethoscope test.....injectors working on all four. have not grounded the plug yet, but i dont think thats the problem because i have swapped plugs and coil packs that i know are working from other cylinders

[sepulchral]

take off your valve cover you may discover your rocker arm could have fallen off or something