What would be the effect on engine operation of an air leak in the intake pipe for one cylinder?

What would be the effect on engine operation of an air leak in the intake pipe for one cylinder?

• A. The engine would stall immediately.
• B. That cylinder would run lean and detonation could occur.
• C. The engine would run rich.
• D. There would be no effect.

Answer: (B)

When a leak sits in the intake for a single cylinder, extra air is pulled into that cylinder without a corresponding increase in fuel. That shifts the air-fuel ratio for that cylinder toward lean. A lean mixture burns hotter and can raise peak temperatures and pressures, increasing the chance of detonation (spark knock) under certain operating conditions. The engine doesn’t suddenly stall or run rich because the leak adds air, not fuel, and it affects only that one cylinder, though you may notice rough running or a misfire. So the cylinder would run lean with a risk of detonation.

When a leak sits in the intake for a single cylinder, extra air is pulled into that cylinder without a corresponding increase in fuel. That shifts the air-fuel ratio for that cylinder toward lean. A lean mixture burns hotter and can raise peak temperatures and pressures, increasing the chance of detonation (spark knock) under certain operating conditions. The engine doesn’t suddenly stall or run rich because the leak adds air, not fuel, and it affects only that one cylinder, though you may notice rough running or a misfire. So the cylinder would run lean with a risk of detonation.