01 Ford F150 5.4 Multiple Misfires

Sorry about the long post, but I think it’s important to add all details when asking for some help. 2001 Ford F150, 5.4, 8-Cyl, 2-Valve, 160k miles. This vehicle had spark plugs changed by someone (not a shop, but by “former ford technician”). This individual forgot to torque down the plugs on Cyl 8 and 6 and they blew out when he cranked the engine. The ignition coils were damaged, as well. Luckily, the threads were not damaged. He torqued down the plugs and vehicle owner no longer wanted anything to do with him. The owner witnessed the entire ordeal. Owner also stated that PCV valve and Fuel Filter were replaced (Motorcraft brand), and Seafoam was poured in the fuel tank to “clean out the engine”.

When the owner drove it home, he could feel random misfires at idle. Owner also stated that vehicle ran beautifully before the spark plugs were changed. Once I got a hold of the vehicle, I noticed that the misfires are prominent only at idle, and they’re not dead misfires. It’s a low-intensity stutter with an occasional “thump”. Also noticed that engine smooths out when vehicle is put in gear and driven. I looked at the power balance test on my scan tool, and I was able to see misfires on Cyl 5, 6, 4 and specifically more on Cylinders 7 and 8. Whenever I feel a “thump”, I see an increased drop on Cyl 7 on the power balance test. Issue seems to be centralized on on bank 2. I pulled out the pico and did a relative compression test, twice. Relative compression test showed a clean, uniform pattern. Also used a secondary ignition paddle to look at firing lines, but all cylinders looked the same with no abnormalities. Since the ignition coils were replaced with aftermarket Accel coils, I went ahead and tapped into the ignition coil fuse with a current probe. Nothing stuck out to me, so I decided to inspect the spark plugs. When I removed a spark plug, I noticed that the threads were caked in anti-seize. Knowing that some of the spark plugs had blown out and re-used, I decided to run a thread chaser in all 8 cylinders, and replace all the plugs with Motorcraft brand.

Unfortunately, the vehicle is still misfiring. The same cylinders were misfiring (Cyl 5, 7, 8 and sometimes 4). I placed an pulse sensor in the tailpipe to verify the power balance test accuracy. I found that the power balance test was reporting misfiring cylinders accurately. I checked fuel pressure and even did an injector balance test. Fuel pressure is within spec and injectors measured the same.

Fuel trims remain under 6%, so I don’t feel that it’s a fuel delivery issue. In fact, fuel trims on both banks are identical. I did notice slightly elevated fuel trims under load, so I cleaned the MAF sensor just for good measure. O2 sensors on both banks are working properly and voltage readings are also identical. There are no codes in memory, but I did catch the MIL flash once while test-driving it. I had a scan tool connected and a pending P0302 was stored. After the test-drive, the pending code cleared on its own. Mode 06 showed some misfire counts on Cyl 2 and Cyl 7. This vehicle has a vacuum-operated EGR system. Concerned about EGR gases possibly passing through at idle, I checked the EGR vacuum solenoid operation with a vacuum gauge and bidirectional control. It’s sealing at idle. Also disconnected the EGR tube that connects directly to the EGR valve, to verify if EGR valve wasn’t sticking slightly open at idle. Nothing wrong with the EGR system, Although I have access to advanced diag tools, I lack experience. I worked at a shop for a couple of months and did some diag work, but this one is kicking my butt. Data is pointing me towards a mechanical issue, but relative compression looks good. I don’t have enough data to call it a mechanical issue. I don’t have an in-cylinder pressure transducer either, so I went ahead and ordered a compression test kit. The multiple misfires were sidetracking me, but I think I need to zero in on this cylinder 7. I’m trying to gather as much data as possible. Anyone with experience with these 5.4 engines will be greatly appreciated. I've attached some waveform captures and videos.

Ford Power Balance Video
Ford Live Data Video

Can you share your Pico files?

Chad wrote:

Can you share your Pico files?

Of course! You'll have to download them from my Google Drive. I've added the link below. The files are too big to be uploaded here.

Pico Files download

jm_460 wrote:

Owner also stated that vehicle ran beautifully before the spark plugs were changed.

It's highly unlikely the work previously performed by Bubba was routine maintenance............

jm_460 wrote:

Data is pointing me towards a mechanical issue, but relative compression looks good. I don’t have enough data to call it a mechanical issue. I don’t have an in-cylinder pressure transducer either, so I went ahead and ordered a compression test kit.

That RC isn't smoking gun bad but there are repeatable patterns in it. Not enough evidence to call mechanical but justification for further, billable, testing. Since you have a piezo maybe try it on the intake and crankcase. And if you get to the point you need to go in cylinder there is a thread somewhere on here showing how to use junkyard AC pressure transducers for that.

Matt T wrote:

jm_460 wrote:

Owner also stated that vehicle ran beautifully before the spark plugs were changed.

It's highly unlikely the work previously performed by Bubba was routine maintenance............

jm_460 wrote:

Data is pointing me towards a mechanical issue, but relative compression looks good. I don’t have enough data to call it a mechanical issue. I don’t have an in-cylinder pressure transducer either, so I went ahead and ordered a compression test kit.

That RC isn't smoking gun bad but there are repeatable patterns in it. Not enough evidence to call mechanical but justification for further, billable, testing. Since you have a piezo maybe try it on the intake and crankcase. And if you get to the point you need to go in cylinder there is a thread somewhere on here showing how to use junkyard AC pressure transducers for that.

I'll hook up the pulse sensor to the intake & crankcase. I'll report back once I get around to doing it. I looked up the DIY AC pressure transducer. Thanks for letting me know. Looks very easy to do & inexpensive. Defi itely worth a visit to the junkyard.

So, I managed to scope the intake with the piezo sensor. I didn't have a hose large enough for the crankcase test, so I'll try it this weekend. Something that I didn't mention was that this vehicle was brought to me several months ago. I couldn't find the issue, so the owner said it was ok since the vehicle was hardly driven, and that he was going to worry about it later. He began driving it recently, and the misfire issue has been getting intermittently worse, which is why it's back in my hands, once again. While looking through my pico files, I was pleasantly surprised to find saved intake and exhaust pulse waveforms from that vehicle. I forgot that I had saved them several months ago. Well, this time around, the intake and exhaust pulse waveforms looked very different from the original waveforms. Initially, they looked good but gradually got worse. Intake looks ok at idle, but falls apart when a clear-flood crank is performed (same with the exhaust side). I also probed primary side of the ignition coil #1 and compared it to the cylinders in bank 2. I noticed quite a bit of turbulence in the spark firing lines in bank 2, especially on cylinder 7 (the cylinder that has the highest misfire counts of all). This is a mechanical problem, but I'm seeing faults in both the intake and exhaust waveforms. Both banks seem to have faults? It's hard to say exactly what the fault is, since this is the first time I've ever caught a fault with the piezo sensor. I think it's time to build an in-cylinder pressure transducer and see what interesting waveforms I can capture.

That intake waveform is strange. Was it taken on the EVAP purge line or somewhere else? Manifold looks like it might be dual plane and hooking in after the planes split will give a waveform like that.

Yes, I went for the evap purge line. Unfortunately, I'm afraid that you are correct. After taking a look, I found that this intake manifold is dual plane.