85thunder

miss from idle to about 2000 rpm, code 304 says missfire on cyl 4, replaced spark plugs, wires, and coil pack. unhooked and plugged pcv valve at manifold, unplugged egr valve, also ran with MAF sensor unhooked with no changes. Can unplug wire 4 at coil pack with no rpm change, unplug 2 or 3other plugs at same time will slow engine, then plug and unplug cyl 4 with no change, unplugged injector 4 with everything else hooked back up and no rpm change, then unplugged injector 5 and 6 - rpm slowed, unplugged injector 4 with 5 and 6 and no change, cyl 4 plug is hot and dry when removed after running engine, moved injector 2 to cyl 4 and still no change, still pulls cyl 4 missfire, and injector moved to 2 will slow the rpms when unplugged now, probed wires on injectors and all light a test light, sprayed the manifold with starting fluid around all injectors, ports under manifold ect with no rpm change, whew!!! that even makes me tired, I know this is a lot but I am almost to the jumping off point .. taking it to the Ford dealer, ouch one tech recommended removing intake and checking for cracks in plastic or gasket seals, next step unless you guys can help soo heeelp, thanks

Hangwire

Sounds like you have gone through a very thorough process of checking things and you've eliminated alot of things. I would suggest editing this and structuring your sentences and making this post a lot more readable. Run on sentences and awful grammar like that will discourage a lot of people from responding or reading your post.

Moonshine

Compression tested?

WhiteFoxGT

Seems as if you have all the basics tested... fuel and spark seem to be ok. Only thing left is valvetrain and the piston. Do a compression test... you could have a damaged valve or piston

85thunder

Sorry I left that out, compression was 85 to 100 psi on all cylinders, after replacing intake gaskets, same miss,
However instead of cyl 4 miss fire it pulled missfire on cylinder 3 this morning.
At lunch switched injector 3 with number 1 with no change,

cliffyk

85 to 100 psi compression is quite low--100 to 134 is the lowest acceptable level shown in the '03 shop manual, don't know about the '98.

Did it build up slowly during cranking (rings) or stay at the same reading more or less (stuck/worn valves)?

DRAGUL

Not sure if this helps but a few months ago i had a similar problem on my truck. Scanning it would read misfire code and everything checked fine. What it ended up being was a slight coolant leak at that cylinder. Bad head gasket. When the engine came up to temp the plug would start misfiring. Keep an eye on your coolant level and see if there is any change.