97 blazer misfiring cylinders

[cyclonesisu2004]

misfiring codes p0300 on cylinders 4 and 6, have codes from 10-40. fuel pump was changed and new spark plugs, plus fuel injectors tested ok, what else may cause this misfiring

[OverBoardProject]

Try - checking timing
- hook the timing light up to the misfiring plug leads, see if the light skips a beat.
- Taking off distributer cap, and cleaning all contacts, including router
- wiggle the distributer shaft... the bushings could be worn out
- If that doesn't work you might have to replace the distributer cap, or plug wires

[cyclonesisu2004]

Thanx for the reply. While replacing the distributer cap, should the router be replaced too to insure best performance or will cleaning do the job?

[OverBoardProject]

I would usually replace the router with the cap, however at the price that I'm sure a new router costs it's probably worth trying to clean it first. If it still acts up replace the router

[cyclonesisu2004]

final touch- ive replaced the distrib. cap, plug wires, fuel pump, spark plugs, fuel filter, and guess what........ same thing. so i did some research, and found that the fuel injectors are known to plug constanly, or may go out at an early age, so what im wondering is this true, and if so why dont more people know about it????

[BlazerLT]

first off, replace your rotor with the new cap ALWAYS.

Sounds like you need to replace both injectors going into 4 & 6 or have them ultrasonically cleaned.