2001 Expy Knock on acceleration

[VictorDuwon]

Howdy everyone,

I have a 2001 Expedition 4.6L XLT, rwd, 186K miles. A few weeks ago, while driving, I heard a thump toward the front of the vehicle, then the knocking started. It is a definite metallic knock which only occurs above 1500RPMs while accelerating. I was doing ~20-30mph at the time. When I let off the accelerator, the knock went away. The truck did not throw a code until I got home, then it was P0301.

So, I opened her up, and replaced the #1 plug and COP. [I bought a full set of plugs and COPs a few years ago, and had leftovers.] The knock persisted.

Next, I replaced the #1 fuel injector with a new one. The knock persisted. Not only does the knock return whenever I accelerate, but after a few minutes the P0301 returns too.

To clarify, it is definitely a p0301 and not a p0300. I've replaced all the components there, and don't know what else to do. This is my daily driver. I'm a decent shade-tree mechanic, but this is straying outside of the things I know how to do. Any advice would be appreciated.

TLDR;

Truck : 2001 Expy 4.2L 186K Knocking on passenger side of motor
Symptoms : The knock can't be heard while the engine is idle, only on acceleration over 1500RPMs.
Low speed acceleration - Knocking
Coasting regardless of speed - No Knocking

Unsuccessful attempts to fix the P0301/Knock:

-Replaced plug
-Replaced COP
-Replaced Fuel Injector
-Fresh Oil/Filter change.

 

[00XTL]

If you cant hear the knock while in the vehicle then pop the hood and remove the 4.6L engine cover. With the engine running and in park use the throttle body to rev the engine and listen for the noise. If you can hear it the get a stethoscope if you can or a long screw driver and place it in different spots to hear the noise more clearly. It’s coming from the bottom end that put your listening tool up to the oil pan or where the oil pan and engine meet. If you cant hear it the try putting the truck in gear and power braking it.

You can also use a screw driver and listen to make sure the injector is working.

If you do all that and still no knocking then i would focus on why its miss firing

 

[VictorDuwon]

Thanks for the response 00XTL. I can hear the knock inside the vehicle, however when I have it in park or neutral, I hear nothing inside or under the hood. Its only present when moving under acceleration above 1500rpms. I bought a stethoscope as you suggested and there is a regular tap from the #1 injector when I put the probe at the base of the injector. It is loudest when touching the #1 injector and less noticeable, when repeated at the other injectors. It is not the rapid knocking I hear under acceleration, but more of a scaled down tap-tap-tap.

The #1 injector is less than week old by the way.

 

[JamaicaJoe]

Sticking exhaust valve?

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[VictorDuwon]

Thanks JamacaJoe. Is there a way I can verify that? Would that coincide with the P0301 code that keeps returning. It is the only code that gets thrown.

 

[JamaicaJoe]

I am just throwing that out there as the engine can log a misfire for any reason including loss of compression on a cylinder. Under load conditions are going to stress things so, if the exhaust valve is gummed up or has a weak spring it may dwell a bit longer.

What you are complaining of is disturbing enough that I would recommend removing the valve cover to inspect the valve train and also a borehole inspection of the cylinder.

Also have the oil pressure measured.

Get it towed in , don't risk damage.


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[Trainmaster]

I assume is a knock knock knock and not a single knock and that the P0301 comes back. And that would mean it's in the motor. A single knock can be in the drivetrain, possibly the driveshaft slip joint in need of lubrication. If that were the case the code would be a coincidence.

If it is in the engine, I'd go with 00XLT's advice. You have to find out if it's valve or lower end related. As JamacaJoe said, it could be a valve. Or it could be a rod. You can take off the valve cover and check valve springs, etc. Then you follow the routine to check valves using compressed air and all that stuff...

A knock's not good.

 

[VictorDuwon]

I agree Trainmaster, the knock is bad. I have some supplementary information. Driving today @60mph, on cruise control, the RPMs jumped to over 3000, the CEL began to flash, the knocking was fast and higher pitched, and there was an intermittent thunk separate from the knock. This sound came from what felt like, the driver’s side but low, beneath my feet. The ride during this ‘fit’ was rough, then another random thunk, and the RPMs went back to normal. The code thrown was still P0301 [CYL#1Misfire]

I have my Chilton manual, and will start learning how to remove the valve cover. Thanks for the advice. If anyone has any pointers for doing this job I’d really appreciate it.

 

[Trainmaster]

Valve cover comes right off. Just a lot of stuff to get out of the way. Watch a couple of videos about cam followers. They break and/or fall out or jam up. You'll want to look carefully at them for wear or damage when you're in there. Thant's one thing that can jump out of place, hold a valve open/closed then jump back in. Not too hard to fix.

A broken valve spring may be hard to see.

A longshot: If you didn't use a Motorcraft coil, you might try swapping your new #1 coil with another cylinder. Many cheap ones are bad out of the box.

 

[VictorDuwon]

I'm researching Cam Followers, and how to remove the coolant hoses and other obstructions. I will begin working on it this afternoon and update here. Thanks again.