2010 5.4L Hard Cold Start and Buzzing noise from driver’s side bank after warmed up (video)

[OffroadMT]

Hey everyone,

I’m hoping to get some advice on an ongoing issue with my 2010 Ford Expedition 5.4L Triton engine with 201k miles on it. The problems started after a particularly cold weather last year, and I recently replaced the spark plugs, hoping it would finally solve things, but the issue still persists. Even though the sparks were in horrible condition (0.080 gap) Here’s what’s going on:

When the engine is cold, it’s really difficult to start – it takes several attempts, and I have to hold the throttle open to keep it from stalling. I have to rev up to around 3000 RPM to keep it running initially, then gradually backing off as it starts running smooth. Once it’s a little bit warm, it idles normally, but without that initial throttle input, it dies out quickly.
Through the scanner I also noticed that the Flex Fuel Percentage was very high ~80%. I cleared it and it risen to 20% since reset. I use 87 gasoline from Costco with up to 10% ethanol in it. So far I found that fuel system might be loosing prime. I'm wondering if some of my injectors are flooding the cylinders with fuel when my truck is just parked. But the issues are not happening during warm weather, so I'm not sure where to look next.

I’m also hearing a strange buzzing sound from the driver’s side bank that I can’t quite pin down which started after the spark plugs replacement. I’ve tried searching the forum and reading up, but nothing seems to match this symptom.

Here is video I filmed after the spark plugs replacement: https://youtu.be/h_SJ-Ly-AKQ

Here’s what I’ve tried so far:

• MAF Sensor and Throttle Body both were cleaned recently.
• Fuel pressure is steady at 50-60 psi before start.
• I double-checked that all the coils and plugs are properly seated and torqued.
• Fuel Treatment: I ran a tank with Techron High Mileage to clear out any potential deposits. Also used isoheet to clear possible water/ice in the winter when issues started initially.

My Main Questions for the Community:

1. What could be causing the buzzing noise from the driver’s side bank? Has anyone else experienced this?
2. Cold Start/Stalling: Has anyone seen similar issues, especially in cold weather?
3. Fuel System or Injectors? Could this be related to leaking or clogged injectors, or even a fuel priming issue?

OBD shows P1000 because of the rough starts, and at some point I have seen Bank 1 & 2 fuel mixture too rich codes but those never appeared again. I’m stumped at this point. I’d really appreciate any insights, especially if someone has dealt with a similar issue on the 5.4L Triton. Thanks in advance for any advice you can share!

 

[S20Workstation4]

Not sure what the buzzing noise is....but I would set that as the last thing to diagnose.

To test if the injectors are leaking while sitting, leave the car sitting for a couple of hours, then remove the spark plugs from each cylinder, and smell for fuel. An un-burned fuel smell indicates leaking injectors.
I would start there.


Joseph

 

[TXResponder]

A rough start and that mechanical buzz like that video sounds like a fuel issue. I'd suspect your injectors if your pressure holds solid while starting. That buzz is fuel injector noise. The comment above has the test for checking if they're leaking, but they could just be obstructed as well.

Although more unlikely, if you lose fuel pressure and then it rebuilds before starting I'd start suspecting the fuel pump. In addition, the fuel pump driver module would be a possible issue if it takes forever to prime or just sometimes decides not to. Also you can sometimes just look at it and see corrosion.

Have you ever replaced your fuel filter?

 

[OffroadMT]

To test if the injectors are leaking while sitting, leave the car sitting for a couple of hours, then remove the spark plugs from each cylinder, and smell for fuel. An un-burned fuel smell indicates leaking injectors.
I would start there.

I will check. After everything I checked it all boils down to injectors or fuel pump

Although more unlikely, if you lose fuel pressure and then it rebuilds before starting I'd start suspecting the fuel pump. In addition, the fuel pump driver module would be a possible issue if it takes forever to prime or just sometimes decides not to. Also you can sometimes just look at it and see corrosion.

I can hear fuel pump before every start but I will look at the fuel pump driver state

Have you ever replaced your fuel filter?

No, not in last 6 years. I should change it at this point.

Thanks for the tips! I will look into fuel pump driver, fuel filter and injectors. It starts fine lately even considering the weather got much colder in MT, but I don't think it was fully solved. I will keep trying to find the root cause.

 

[eddytheexpy]

So at the end of the video, I can't tell if those spark plugs are sooty or oily. The parts that are black seem to be a bit too shiny for soot which makes me think that it's oil. If that's the case, one of the ways your plugs can get oil fouled is from excessive blow by past the piston rings. Excessive blow by can cause hard starts and we all know metal expands/contracts based on temp and material properties. I'm thinking you've got a not-so-good amount of blow by in temperate weather up through operating temp. However, when the outside temp drops, that gap grows (both components are at the same temp but are of different materials so different expansion coefficients) and can't contain enough pressure at cold idle to actually run. When you open the throttle, it creates enough expanding gas per unit time to compensate for the blow by and once you've done it long enough to warm up those components, the gap closes to a sustainable level.

Long story short, a compression test (with the engine cold and outside temp cold as well) would be an awesome thing to do.

Also, I second S20Workstation4's comment. Figure out the stalling issue first before worrying about the buzzing. But if you're looking for extracurriculars in the meantime, pick up an automotive stethoscope to chase that buzz. If you find it, don't spend money on it until you've confirmed the stalling problem is financially feasible to address.

good luck! Fingers crossed that it's not the blow by issue!