I have a 99 expedition, 5.4 with 4X4. We pull a 6,000 lb travel trailer. when pulling up a grade the engine sounds like a tin can with rocks in it when you shake the can. I started using premium and the condition lessened. Now it happens less but the engine still will do it under extreme conditions, 3500rpms or so. All the cops have been replaced and it is tuned up. It has 155,000 miles on it. I read somewhere that a bad timing chain may cause this sort of problem. I was hoping that someone may have run into this probem. It is rated to pull 7500lbs., so we are at the upper limits of its tow capacity. Another problem started last week. A chemical smell and vapor come from the vents when the heater or air is on. It has a smell like antifreeze. Any ideas on this. On the timing chain any ideas on the cost to replace. Thanks in advance. Bob
Exactly as fixit5561 said, heater core! While you are doing that I suggest that you replace the blend door also, as that is a common failure. A good radiator shop will charge about $450.00 and do both. If you get a better price tell the world as there are sure to be others in your area that will need this done this winter.
Sounds to me like it has nothing to do with the timing chain and more to do with spark knock. If a higher grade of fuel lessened the knocking noise then perhaps you have carbon build up or an EGR problem? Does it run hot while towing? Heat can cause the pinging noise as well.
I tow a 3000lb camper with my 2000 5.4 expedition and it has 148k with no issues except for the lack of power the 5.4 exhibits while climbing grades.
Hopefully someone can point you in the right direction.