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Idahome
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The timing chain tensioners are pumped up hydraulically when you start the engine, on a cold start a worn tensioner takes a minute to pump up, the chain is slack and the engine is out of time. The slack in the chain can cause major wear on the nylon chain guides, which leads to further damage.
Many SOHC engine owners have a secret trick you can press the fuel pedal to the floor and crank the starter for 6-8 seconds, this will build oil pressure early before you start the engine. Apparently the engine will not start with the throttle wide open, which gives the starter a chance to prime the oil pressure. This helps pump up the tensioners to avoid a slack chain.
Ford recommends the LH and RH head tensioners be replaced at 90K miles.
The SOHC engine MUST have synthetic oil and it must be changed frequently or timing components will wear premature.
Now interesting fact I stumbled upon when I purchased a 2014 Polaris Rzr xp1000 back in 2014, it too had a cold start rattle. I knew the sound immediately and was not impressed. Some investigation revealed that Polaris used the same cloyes tensioners in their OHC engines! Nothing like buying a $18000 toy to find out it has issues from the factory with timing chain tensioners.
Year later we bought my wife a 2015 Xp1K, same noise.
The aftermarket came to our rescue and now there are several types of tensioners available. Spring loaded ratcheting tensioners, a Yamaha design works great....but they are large and may not fit the Ford engine. Then there are manually adjusted tensioners where you set the pre load on the chain, lock down the jamb nut and forget about it....no oil pressure needed. This is what we run in our Rzr's and have never had a cold start slack chain rattle noise since.
Now here we are years later you can get stainless steel manually adjusted tensioners for like $40 each........they screw directly into your SOHC engine. Turn the adjuster in finger tight then back out 1/8 turn and lock down the jamb nut. DONE. On the 99 model year SOHC engine you will have to remove the thermostat housing in order to get access to the drivers side tensioner....the pass side is accessed easily through the pass wheel well.
Ford never offered the sport with a 5.0 nor the sport trac, only 4 door explorers from 96-01 had the 5.0. They are all automatic transmissions and came in either RWD or full time AWD.
Hope this helps
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I build custom RBV, specializing in drivetrain conversions, wiring, suspension and complete custom trucks