Hi, all.

In addition to my 2013 F15 twin turbo V6 (love it), I have a 2010 Lincoln Navigator with the 5.4L engine. I bought this vehicle about 1.5 years ago, with about 147k miles on it. Now it has just north of 163k miles, and it has developed a weird problem.

First let me say that this thing has not been in great shape for the entire time I have owned it. I had it checked out before purchase, but most of its issues did not come to light until after driving it for a while. We have constant issues with P0130 and P0150 codes showing up and going away (right now the CEL is out), for example. Over the 1.5 years, we have had the spark plugs and wires replaced, and we have done other things to it as well.

Now to the issue that started on Friday. My wife took a day trip to the mountains, and she reported that shortly after leaving, the Navigator would have a noise on occasion (anywhere from once every 1.5 minutes to once every 15 minutes). She described it as a grinding noise from the engine compartment, and the noise lasts about 5 seconds. She said that it was something that could be felt on the floorboard. I test drove it yesterday, and heard what I would describe as pinging, and I did not feel anything while that happened. I drove for about 15 minutes before I heard the noise, and I noticed that if I let off the accelerator pedal, the noise got quieter, and if I pressed the pedal the noise got louder.

Obviously we're not going to fully debug this issue on a forum post, but I'm wondering where you guys would start with this. Timing chain tensioner? Bad gasoline? Something else?

If the engine were dying or if this was really pinging, I'd think the problem would happen all the time when the engine was under load. It doesn't. It's only once every while, and only for a few seconds.

I'm completely baffled here. I really hate intermittent problems like this.

Thanks for any thoughts.

 

So you're getting upstream O2 sensors out of range. All of the standard 5.4L questions apply: cold start rattle? Tick at hot idle? Oil type and viscosity? Motorcraft filter?

Do you have an exhaust manifold leak? Studs broken off?

 

Check your front wheel hubs (Integrated Wheel Ends - IWE).

Engine vacuum keeps the wheel ends disengaged. There is a check valve that can go bad that will allow the wheel ends to attempt engagement when the engine vacuum drops under heavy load. When this happens you get a terrible noise from the front that can be felt in the floor. This noise sounds like the engine coming apart when it happens, and sounds very much like heavy engine knock. Generally the noise will go away completely when the engine vacuum goes back up, but the noise could continue if the IWE is stripped out.

Easiest way to check is to drive it around in Auto-4. if the noise doesn't appear under heavy throttle, then it is probably the check valve. Auto-4 engages the front hubs, eliminating the problem of them trying to engage while the wheel is spinning.

You can also check with the engine off and the front wheel raised. Try spinning the wheel with the engine off. if you get a ratcheting sound and the wheel spins, then the IWE is stripped out and that could explain why the noise doesn't go away completely when engine vacuum comes back up. if working correctly, the driveshaft and half-shaft should spin with the front wheel raised and engine off.

These are simple checks to diagnose a problem with the front hubs, or eliminate them.