Toyota Repair: Sudden shaking, jerking, loss of power.

Question
My 1991 Toyota Previa has 270,000 miles and is like an old Timex watch "it takes a licking and keeps on ticking"...that is until today. I allowed my  SIL to drive it and while on the Interstate it suddenly started jerking, jumping, shaking and losing power and unable to go any faster than 45 miles an hour. He was able to get it off the Interstate and parked somewhere safe until I can get it home this weekend. Do you have any idea what the issue or issues might be? I've had this van for about 10 years and when I bought it there was a loud rattling noise coming from underneath it and it still makes the same noise. No one has been able to find the reason for the noise and it has not interfered with the performance; just sounds bad.Don't really think its related to the currant problem after all these years but did want to mention it. Thank you for any help you can supply.
Sheila

Answer
Hello, the rattling noise is typically loose baffles inside the catalytic converters and is probably not related unless the baffles finally came loose and clogged exhaust gases. Other than that it's hard to say what caused the symptoms you mentioned, possibly a misfire, bad spark plug, distributor cap, rotor ,let me know when you get it back and we can continue from there.