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Ask ironmike Your Own Question
Category: Lincoln
Satisfied Customers: 3385
Experience:  30 years, Ford master certified
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My 2003 Lincoln Navigator lost acceleration power and is now

Customer Question

My 2003 Lincoln Navigator lost acceleration power and is now in the shop. The mechanic can't find anything wrong with the computer. It will start but is running really rough on one side. What could it be?
Submitted: 1 year ago.
Category: Lincoln
Expert:  ironmike replied 1 year ago.


Did the mechanic verify the valve timing? this engine has cam shaft phasers that change the valve timing and they can fail and cause one bank or cylinder head to have misfires. With the dealerships diagnostic tool(IDS) they can watch cam timing advance and compare each side. usually with your symptom you will see a big difference on the side not firing right. It is also possible the chain jumped. Let me know how many miles and if the engine makes any noises.

Expert:  ironmike replied 1 year ago.

The 5.4L 3 valve engines use oil pressure to operate the VVT(variable valve timing) system. poor maintenance can effect the operation and things just fail with mileage. They do not always set codes when issues like this happen. Most common cause would be a bad phaser, not that bad to do or not too expensive. Let me know what you find . You can tell the shop to check the actual and desired bank 1 and 2 valve timing on the IDS.

Expert:  ironmike replied 1 year ago.

after market is much cheaper than ford/Lincoln.

Customer: replied 1 year ago.
Mileage is 255k
Expert:  ironmike replied 1 year ago.

wow! not too many last that long. Must be highway miles. Have you replaced the phasers, chains or tensioners?

Expert:  ironmike replied 1 year ago.

you must do regular oil changes, that is the key for this engine.

Customer: replied 1 year ago.
My daughter is driving it and I am pretty sure she has not done either. Miles are mostly highway
Expert:  ironmike replied 1 year ago.

All I can say is wow. highway helps , best for an engine.

Expert:  ironmike replied 1 year ago.

if the vehicle is still in the shop let me know what they find. I use a phone APP that shows live data like this. Torque pro from google play. I use it on my phone with an OBD2 Bluetooth adapter. less than 40$ for both.