2010 Ford F-150 (5.0L) Cylinder 4 Misfire

Justin Diagnostician Morrisville, Pennsylvania Posted   Latest  
Question
Driveability
P0304 - Cylinder 4 Misfire Detected

Hey all, first time posting here. Wish I discovered the site sooner, great resource!

I have a 2010 F-150 5.0L in the shop that has a #4 cylinder misfire. It is not a dead miss, but pretty regular and sets a P0304. 

#4 exhibits about -20 to -40% low contribution via cylinder balance test at idle (ran on an Autel MaxiSys). With the cylinder disabled it drops down to a steady -80%. Swapped #4 coil and plug with Cyl #1 and the miss stayed put at Cyl #4. Did not move.

I am a pretty new scope user, but I have ran a relative compression test which looked just fine. I have also scoped the injectors, again all looked fine (at least I think they did. All 8 cylinders were pretty much identical). 

Upon scoping the secondary ignition though I found something unusual. Ford uses a multi-strike/spark ignition strategy at idle and on the trouble cylinder the second firing looks odd. The burn line from the initial firing stays straight as an arrow directly into the second firing. The spark also looks weak as compared to a good cylinder as well, but to be honest I'm not sure if that's just down to my scope settings or not. Waveform is similar even with a swapped coil and plug. Wondering if this could be my issue? 

Appreciate your time, have a safe Holiday weekend!

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Curtis Mechanic
Lakeland, Florida
Curtis Default
 

Check out this u tube guy, fordmacayouloco, this guy is real spot on, I watched a vid on that and type of misfire, he pulled valve cover while recording too show one of the lifter rockers pop off says common problem, hopen this helps

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David Owner/Technician
St. Albert, Alberta
David Default
 

Do a leak down on #4. Valve problems are too common on those things too.

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

Will do. Both you and Jeff have mentioned the valve problems being an issue. Good to know, thanks!

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Marlin Technician
Estacada, Oregon
Marlin Default
 

It is very obvious that an electrical fault is present. Where the transistor should be grounding the circuit, you can see what appears to be arcing followed by a very small drop of voltage. There is a faulty connection, inside or outside of the PCM. Should be a simple thing to test and to determine what needs to be replaced.

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Curtis Mechanic
Lakeland, Florida
Curtis Default
 

JUST ASKING, have you seen this on ur scope and please explain that is new to me🤔

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Marlin Technician
Estacada, Oregon
Marlin Default
 

I don't recall ever seeing anything quite like it. I need clarification- what did you use to get this capture? I assumed that you had the scope connected to the primary circuit, because that is what it looks like.

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

I used an old school clip-on secondary probe. The engine uses coil-on plug but I have an extension I use. Unplug the coil, connect the extension between it and the plug, then clip on the secondary probe. Barring any mechanical issues (heve yet to do a leak down test) I am thinking it may be a PCM issue. The initial spark looks good but that second firing looks like something is shorting out…

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Marlin Technician
Estacada, Oregon
Marlin Default
   

Something is weird with your set-up, because burn lines on both cylinders are too flat. Whatever the case, scope the primary side next. This will show exactly what is going on their, and whether or not control is the problem. I am quite certain that it is a primary circuit fault, and it definitely is not a mechanical fault. With that, I am off of here for the weekend!

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Don't stop with your secondary test. Go and get a current & voltage wavefrom from that cylinder, as well as a known good cylinder. Also, take a look at the fuel trims to see how the PCM is reacting to this misfire.

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Jeff Technician
West Columbia, South Carolina
Jeff Default
 

wheres the in cylinder compression capture? And did you do it running or cranking? Bad valve seat may only show up on cranking compression waveform. You can also put a transducer in intake and you will see every intake valve event. Or old school it and do a leak down test. Also is that primary or secondary ignition waveforms? And does the scale say 10mv/ division? Either way, remember that if…

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Curtis Mechanic
Lakeland, Florida
Curtis Default
 

Fordtechmakayouloco I think that's the right link

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

He spells it "makuloco" you can google just that, and find him

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

Unfortunately I do not own a pressure transducer. Next on my shopping list, though! It is a secondary ignition waveform, and the scale does indeed say 10mv/div (which is why I was unsure of the results). I know I should be looking at kvs rather than mvs, but I did not see any options for the probe I was using (an old school clip on secondary probe with a COP extension/lead), so just ran it as…

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Jeff Technician
West Columbia, South Carolina
Jeff Default
 

Buy an old three wire gm map sensor and rig up a 5 volt reference source ( I use a snapon battery for a heated jacket and a usb cable using only the 5 volt power and ground wire) you can research and find voltage to pressure charts on whatever sensor you’re using if you want but it isn’t that important. If it is a bad valve seat you will see an increase in manifold pressure while the cylinder…

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
   

Hey Jeff, just did a little more research on the probe I was using and apparently it is an x10000 secondary ignition probe. I believe that means that even though the scope shows mv/div what we are seeing is actually kv/div.

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Jeff Technician
West Columbia, South Carolina
Jeff Default
 

looks like an Autel scope, are you using the scan tool or the pc version?

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

It's the 4-channel Autel scope (came with my MaxiSys scanner). I'm using it on a PC because it frees up the scanner so I can bounce between cars (busy shop!). Also there are a lot of functions available on the PC software that just aren't there on the scan tool. I actually thought the scope was very basic in functionality until I tried it on the PC, turns out it's pretty dang good!

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Jeff Technician
West Columbia, South Carolina
Jeff Default
 

I use mine the same way, and you’re right, pc function is better but I’m still saving up for the new pico

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Philip Educator
Hemet, California
Philip Default
 

Lots of good thoughts here and I agree, your primary pattern in #4 is pretty strange. However, I always start looking at a misfire by comparing bank to bank fuel trim. If it is ignition or mechanical you should expect to see the banks within maybe five points of each other. If it is fuel, you will see a significant difference between banks. Since you don't have a circuit code for the coil or the…

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Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

Fair point with the fuel trims, did not think to check them. Will certainly do so Monday morning. Thank you!

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Stephen Technician
Gallatin, Tennessee
Stephen Default
 

I’m wondering how your scope is connected. However, i don’t see any appreciable energy in the initial firing line of #4. The lack of drop down at the second dwell event, I think, shows no current draw. The initial dwell shows a deeper pull down than #1. I would use a current clamp and a primary voltage connection to see if that coil is actually using any power. A secondary capture of that coil…

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Paul Mechanic
Harvey, Illinois
Paul Default
 

Doesn't the scanner support relative compression test. Always verify mechanical when chasing misfires-took me a while to discipline myself also, but saved a lot of headaches later. I would just scope primary, but remember to use an attenuator to protect scope. You can also current probe coils if you can find a common fuse or grouping to compare the good to the suspect one so you can watch on…

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Justin, If you want to learn about how to interpret ignition systems on your scope there is no one better to learn from than Mac VandenBrink. An internet search for, Mac VandenBrink ignition, will get you a lot of places to look. I have included some links to get you…

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Helpful
Justin Diagnostician
Morrisville, Pennsylvania
Justin Default
 

Wow, great stuff! Thanks Eric.

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Justin, Be aware that his teachings are older and based on fuel and air being combined in the intake manifold and then drawn into the cylinder. Some of what he teaches does not match with how a direct injected engine will act when viewed with a scope. One example would be restricted intake air flow where the restriction is caused by carbon build up on the back of the intake valve. Since the…

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Glen Owner/Technician
Arthur, Illinois
Glen Default
 

Justin, Please check your YMM. Are you sure it is a 2010 F-150 5.0L?

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Felix Technician
Miami, Florida
Felix Default
 

check your rear O2 sensor to see if you got a lean misfire , because I just did a ford edge 2011 last friday with the same code and that was the way I did find that that the cause was a injector, the bank 2 was below .100 mv and the other bank was ok, hope this help

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Kevin Owner/Technician
Kennesaw, Georgia
Kevin Default
 

Check for intake follower intake that has come out of it place. Compression and idle quality will be good as one of the intake valves will still be operational. This will usually cause intermittent misfires off of idle. The bearings in the follower will wear causing it to wear and be shucked out of position. There are updated followers to improve this condition. Just need to verify cam lobe…

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