A rough idle and even an emissions inspection failure for high HC and CO can be caused by improperly adjusted valves. Also, exhaust valves may become to tight which can lead to valve failures. Our technicians tell us that regular valve adjustment inspections are a must.
Improperly Adjusted Valves May Cause Emissions Failure/Rough Idle on Toyota 4Runner
Average mileage: 221,617 (180,000–289,000)
9 people reported this problem
3 people shared problem details
1999 Toyota 4Runner289,000Visitor
rattle on acceleration maybe valves
1992 Toyota 4Runner195,853Visitor
Idles poorly but runs well at higher RPM's. Won't pass smog due to high hydrocarbon reading.
car runs rough and smells like something is burning after driving just a few miles. It has bee...
i took it back and the mechanic said i needed a valve job. 1,200.00. it accelerates fine but as...
where is the idle screw located?
I read the manual and the idle is supposed to adjust automatically.
It idles like 1500-2000 when it's cold suddenly. After driving a few minutes it comes down to n...