 I have a 1997 F-150 XLT 4x4 with approx 165000 mi, ran well when just bought but developed a heavy cylinder misfiring issue. This is common with many F-150s especially the 4.6L V-8. I had to take the truck into the shop 3 times to fix the issue and the cause still cannot be diagnosed today. It is still misfiring! I do know that I have to keep changing my spark plugs which are almost impossible to gain access to. The total cost of repairs on this issue is now near $500. Another issue with this F-150 is the 4 wheel drive system. It mal-engages and a I hear a big BOOM underneath the cab. I engage it normally by setting it in neutral and then switching it. Ford must improve their quality!   