2008 F250 5.4 misfire codes

Pickup came in with P0300, P0307, and P0316 but ran smooth. To make a long story short, diagnostic tests seemed to indicate ignition. Customer said another shop replaced plugs 10,000 mi ago. Found cylinder 7 had a different plug than the rest which was very rusty and gap was wide. I replaced the plugs and boots. First drive cycle the codes didn't come back but the second drive cycle they did. Found that under load the check engine light would start flashing and it would quit when I let off the throttle. In park at 3000 rpm the check engine light would start flashing after about 23 seconds, the engine rpm would drop 25 rpm, and when I returned to idle there was a dead miss. After about 30 seconds of idling the miss would go away and the engine ran smooth. This will happen every time at almost the exact same time interval. After this I pulled codes again and had P0300, P0307, and P0308. I installed my spark tester in between the coil and plug on cylinder 7 and then 8. When initiating another miss the ignition never went away. I then installed a noid light in the injector connector for cylinder 7 and I lost injector pulse with the miss. Is there anything else I should check before I condemn the injector driver?

Yea that system may have intentional shut down. I know a 2010 escape 4 cylinder I just worked on did. What does mode 6 say?

The injector shutdown may be the ECM deliberately disabling fuel to the misfiring cylinders. Have you tried swapping the coils around yet to see if the misfires follow them?

I don't lose ignition on either cylinder. I did replace the coil on cylinder 7.

I agree with the above, injectors are likely being shut down on purpose to save the cat.
Sounds like you're maybe using one of those bulb style spark testers?
If so, it doesn't place sufficient load on the ignition system to flush out a weak or borderline coil.

This is the only tool I trust for that job.
I am also very skeptical of Ford misfire codes and usually end up testing them all to make sure I don't miss one get ready to crap out.

My scantool isn't a rockstar on this particular model, doesn't give me some live data I want to see, in conjunction with my lack of experience in diagnosing these types of issues equals the worst of both worlds. What I can make of mode 6 is I have misfires on 7 and 8. There is more stuff I don't understand. I can take a snapshot tomorrow. It would help to know what you want to see from mode 6. This stuff is a completely different animal from the diesel world. I have customers that are relying on me and I need to learn it.

I am using the bulb style. If the injectors are shutting down to save the cat is the issue in the cylinders that the injectors are shutting down? All plugs and boots are new. The coil on 7 is new. The one cylinder that has thrown codes the whole time is 7. I didn't get codes for 8 until I pushed it hard. I'm not sure what to do with this thing at this point.

fixn_junk wrote:

I am using the bulb style. If the injectors are shutting down to save the cat is the issue in the cylinders that the injectors are shutting down? All plugs and boots are new. The coil on 7 is new. The one cylinder that has thrown codes the whole time is 7. I didn't get codes for 8 until I pushed it hard. I'm not sure what to do with this thing at this point.

It's going to kill the injectors on the cylinders it thinks are misfiring. So, if it's wrong, it's going to kill the wrong injector. The misfire counter isn't always wrong, I've just been bit enough to not trust that it's not always pointing to the only cylinder with a problem.
The adjustable spark tester stresses the ignition coil in the bay like when you go out on the road and push it hard. #8 coil could be marginal and only failing under load.
Like Matt said, try swapping #8 coil to another cylinder and see if the misfire follows.
Ideally, move it to a cylinder that isn't next in the firing order.
The firing order is 13726548, I would probably move it #5 since it isn't the companion cylinder to 8 and it isn't adjacent in the firing order.

Aside from the ignition system, is the misfire felt constantly or only under load, or only at idle?Have you thought about a compression test in #7 since it's the one coding most often?
You've probably seen Scanner Danner do a clear flood crank where you hold the gas pedal to the floor to disable the fuel system and give it a long crank listening for any kind of uneven sound in the cranking cadence that would point to a compression issue.

I see what you are saying about the misfire counter.

I have not seen the clear flood crank yet. I've only watched a handful of videos so far. I plan on watching them all but only have so much time.

There is no misfire felt at all until the injectors are cut out on 7 & 8. It runs real smooth until that point at low idle, high idle, and under load. I also do not get codes for 8 until the injector cuts out. Fuel trims hang to the positive with bank 2 running a little more lean, 2-5 short term and 5-7 long term. Running down the road the short terms both run pretty close to 0 but long terms stay around 5. I was thinking about doing a compression test on 7 last night. I will get it back in to do a compression test and swap coils.

I am using Auto Enginuity and it's a little frustrating on this pickup because it doesn't give me the option to monitor misfire counters in live data. I have to go to mode 6 where I just get a snapshot and I'm not sure what the time parameter is for the snapshot. I will post some of the data that I can pull up. Some of it may be my inexperience with it but it sure gives me a lot more on other vehicles.

I swapped coils on 8 & 5 with no change. I watched a video where he did the clear flood crank. I did that and it cranks very smooth and consistent. It was colder this morning, mid 20's, and I could definitely feel the misfire at cold startup, and it got less noticeable as it warmed up. I figured out how to refresh my mode 6 data following different conditions, so I have some better info. I have misfires on 7 & 8 at startup and low idle. It gets exponentially worse at 3000 rpm with no load. I register virtually no misfires while power braking. Prior to my original post I also tried the brake cleaner while watching short term fuel trims and then smoked it with no signs of vacuum leak.

Freeze frame data for P0307 last occurrence.

You try checking the plugs??

I already stated that all plugs and boots are new. I replaced all because the plug in 7 was a different brand than the rest, very rusty, and the gap was wide. Also, in the last round of testing I found the misfiring goes away under load, also stated above. From the research I've done, it seems an ignition related misfire gets worse under load.

Because you have not mentioned it, I take it you do not have a scope. Scoping the cam, crank and coils would give you a much better picture of what happening. Paul has mentioned many times as has Noah that Fords misfire counter is not reliable as you can get mislead to the wrong cylinder or cylinders. You're focused on 7 and 8 and not the possibility of other cylinders.

If no scope, swap the injectors on 7 and 8 and see if misfire follows. Just to rule it out.

fixn_junk wrote:

Also, in the last round of testing I found the misfiring goes away under load, also stated above. From the research I've done, it seems an ignition related misfire gets worse under load.

That kind of sounds the opposite of what you said when #8 flagged a code when you drive it hard?
I'm not picking on you, trust me! I've been beat up by plenty of 3 valve Ford misfire complaints.
It's been my experience that misfires at low rpm that improve with higher rpm are generally mechanical in nature. Typically valve sealing.
Not sure why power breaking the engine would improve the condition. Strange...
I like ScannerJohn's suggestion of moving the injectors just to get it off the table, assuming you don't have the capability to scope test. He does have an excellent track record
If that doesn't effect anything, considering the misfires are on the same bank, I'm always worried about a VCT issue. They quite often won't set cam timing codes for whatever reason.
Here's a series of videos on YouTube that I have found particularly helpful.
(I may not have linked them in the correct order)

I apologize for being too novice for this forum. Some of the responses didn't bother to read all of my postings, probably due to my ineptness. I don't have all of the tooling I would like to because I can't afford it. If anyone actually read my first post on the "Welcome Mat" they would understand my situation. I am good at what I do, diesel and ag. The problem is the drought shut off all ag work here for nearly a year now. I have a family to feed and I am trying to do the best I can, but this type of thing isn't working. I'll just finish the month watching as many videos as I can and save the $11 a month. I apologize for the inconvenience.

I'm sorry you're frustrated, but nobody is getting down on you brother. This forum is intended for everyone regardless of experience.
Those engines can be very tricky.
It's one thing to be there and experience the fault in person and quite another to try to give useful advice over the internet. It's easy to misinterpret someone's intent in this context. If I said anything that you felt was aimed at belittling you or your skill, than I truly apologize.
Nobody here will ever disrespect you for not knowing something, or for not having millions of dollars tied up in scopes and scan tools.
I realize you're out of your comfort zone. That sucks, I feel for you.
If you need to bail, I get it. But this is an inclusive community, if you choose to continue to interact you are most welcome.
Best of luck to you. You CAN do it.

How are you doing on this?

As Noah explains, the network of DIY'ers and experts are here to give you advice and guidance to help solve your problem. Don't feel bad or embarrassed that you do not have the myraid of tool that others have. Part of the ScannerDanner way is to be able to diagnose without those sophisticated tools. Paul can do it with a test light and a multimeter. Some times a test light alone. That's a real professional. I strive to achieve what he's already accomplished.

Please get back to us.

I had to step away from it for a bit. Too much time in it and I need to do some paying work. I plan on bringing it back in today and will update with any findings.

Boy, having trouble with my reply... Understand time is money. Looking forward to hearing more.