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 Supra
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The idle air control motors tend to become carboned up at around 100,000 miles and will cause a...