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lean roll

Glossary “lean roll” Definition:
To turn carburetor idle mixture screws in enough to effect a slight rpm drop, causing a leaner mixture. This can cause the idle speedrise and fall, causing the idle to roll.

lean misfire

Glossary “lean misfire” Definition:
Condition caused by a vacuum leak or open EGR valve, that results in incomplete combustion, causing one or more cylinders to pass unburned fuel into the exhaust system, resulting in an increase in hydrocarbon (HC) emissions.

lean out

Glossary “lean out” Definition:
1). To increase the portion of air or decrease the portion of fuel in an A/F mixture. 2). To decrease the portion of nitro in a fuel mixture.

Lean Burn

Glossary “Lean Burn” Definition:
A Chrysler electronic engine control that appeared in the mid 1970’s. It maintains precise control of the spark timing to allow a very lean mixture to burn properly, reducing emissions using an analog computer.