Is the check engine light lit ? Any DTC'S - diagnostic trouble codes ? What engine ? 4.3 L vortex . Leaking fuel pressure regulator under the upper intake manifold . Leaking fuel injectors ! Ignition timing problem . How does the engine run ? Who installed the plugs an wires ? are they right ? Fuel pressure leak down test, fuel injector balance testing . Check distributor drive gear an slop in the shaft . Did you have distributor out ? Is it in the proper position ? What cylinder is misfiring ? engine mechanical problem ! What do spark plugs look like ? fouled , soaked with fuel . Do a engine compression test .
The camshaft drives the distributor shaft which rotates providing a spark to the correct cylinder by way of the cap and rotor. The camshaft position sensor functions much like the crankshaft sensor previously described but provides only a 1x signal to the VCM. That is, for every 2 rotations of the crankshaft, there is 1 rotation of the camshaft. Note that the CMP sensor will not affect driveability. The sole purpose of the CMP sensor is to provide the VCM with the necessary information for the misfire DTCs.
SOURCE: getting misfire codes for cyl.
it is your fuel injectors, replace them, and the problem will be solved..
SOURCE: misfire after tune up
Since you have a misfire, the fuel in that cylinder isn't burning. Are you sure you have the firing order correct. Also try using one of your old plugs and wire for that cylinder and see if it works. If you only checked for spark at the wire, you might just have a faulty new plug- it happens.
SOURCE: 1997 chevy truck running rough
Is this a 5.7? They are notorious for intake manifold gasket leaks. When mine did it, the diagnostics blamed it on an ignition misfire also! Replaced the gaskets and it runs smooth!
SOURCE: 1998 gmc k1500 random misfires
There is more than just ignition that could be the issue, including fuel injectors and EGR. Try this link to see if you get more ideas:
http://www.engine-light-help.com/P0300-check-engine-light.html
Random/Multiple Cylinder Misfire Detected have a good day !!
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