I'm a new member with a 98 4 Runner SR5 w/3.4l engine which has 197k miles. Mileage has dropped to 13 mpg from 16+/- for winter ops here in Maine. Engine runs slightly rough between 40-50 mph and gets progressively worse to 70+. No difference, in or out of OD. The check engine light doesn't come on. Plugs and wires were changed about 20k ago. Thanks for any help.

 

Roughness has gone away! While enroute to the repair shop it started running OK but had it checked out anyway. Nothing showed up on the scan, no history/no codes. He thought possible EGR sticking or bad fuel. If it happens again I'll stop in and have it checked out. Mileage is back to 15+ mpg.