flewis99

Can anyone steer me in the right direction?
In November my truck started missing or skipping, PO304 code, so I decided to replace all of the coils since my 2003 E150 had a similar issue 2 years ago and coils fixed it. I also decided to replace the plugs and injectors since I would be there anyway. After doing the work I still have a PO 304 code. I decided to take #4 coil out and replace it with the one that came out of the truck. I did ohm out the new one and the older one just to see. The old one pulled around 5.74 and the new one closer to 6, but swapped it any way. Now I still have a PO 304, and developed a PO171 which I know is running rich bank #1. The truck still has an obvious mis or skip, and fuel mileage has really dropped.

Can anyone advise for my issues? I have been working on this issue for almost 2 months and frustrated.

Thanks in advance,
Fred

Turbonut

Start with a compression test, then if needed a leakdown test.

mbb

Well it does depend what kind of coils and plugs you use for starters... You don't want aftermarket you only want OEM.... You should have just swapped the items from a good cylinder to the misfiring cylinder to see if the problem moved without spending any $. But if your problem never got any better at all, as opposed to going away but then coming back, it probably wasn't the coil, plug etc.

I know that manuals will tell you to check the ohms on a coil and that is by and large absolutely useless. Doesn't matter whether it's a car or a outboard motor. 99% of the time these ignition components test good and run okay cold or at idle and only break down when they get hot or under high RPM load. Outboard stators also do same thing. You can basically just forget about any cold, non running tests.

How's your coolant level been? Rock steady for years? Because that's how it should be.

The problem with compression test is they will not always show a small leak. You can have also have carbon buildup that offsets the compression loss, even end up with higher compression in a problem cylinder. But you are looking for anything that's different than the rest.

​​​​​ Is the misfire problem intermittent or always?

BareBonesXL

How did the #4 spark plug look? You can tell a lot from a spark plug.

p.s. people have had problems with the coil connectors. The current needs to pass through the coil for it to work properly.

Dee Veloper

Did you clear the codes between swaps ?

Jbrew

Might of checked spark first. Determine whether it's a the ignition or a motor issue right of the bat. Point yuh in the right direction anyway.

.

Jbrew

If 4 is not firing and you have to drive or run it much, should disconnect #4 injector ... if you want to keep your cats in good shape anyway. Raw fuel from cylinder 4 can destroy them fairly quick. You may even here that happen...yea, not good. Disconnect inj #4..

flewis99

Coolant level always remains the same. The coils that were replaced were 'allegedly' Motorcraft DG508 purchased thru Amazon 2 years ago and about 10K miles. The set I purchased in Nov came from rockauto, not Motorcraft, but with high feedback. Yes I should have spent more time identifying the issue in the beginning, I need to be more diligent in doing that.

Thank you for your reply

Fred

flewis99

Thanks, just learned a lesson about unplugging injector before driving.

Thanks
Fred

flewis99

Honestly can't remember specifically between swaps, but cleared codes many times during the process.

Thanks
Fred