5.4L misfire.

[Charlie_86]

i have a 2003 expedition 5.4 and it keeps having a misfire on cyl 4, now I have scanned the computer and that's what it tells me, it also says misfire upon start up. I have replaced the coil and also the spark plug not only did I replace the plug and the coil I replaced all 8 of them to do the job right and it continues to misfire. I ended up finding out that the intake manifold gaskets were worn out & were sucking in air I went in and replaced that as well but continue to have this issue anyone might know what it can be any ideas thanks? it feels like its never ending with this. Thanks!

 

[CaperCanadian]

A few things i can think of to check. To start check if the plug well is wet, if it is, your jumping spark there, check for voltage to the coil, might be bad wire, have a look at the fuel injector to check flow and voltage, also could be crank sensor.

 

[Skauber]

Did you check the intake for a crack?

 

[madams87123]

If misfire code stays on same cylinder check the fuel injector. You can swap it with another cylinder and see if misfire changes with injector