BMW 750i Check Engine Light – Intake Air Leak
A BMW 750i came in with multiple cylinder misfires and a check engine light. A factory trained technician used a smoke machine to find air leaks at the intake boot and oil cap.
- The engine control computer showed errors for misfires and a lean condition, pointing to an intake air leak as the likely cause. The technician connected the intake system to a smoke machine to locate the source.
- Modern German cars have a sealed crankcase connected to the intake system, so a leaking oil cap causes a lean condition just like a direct intake leak. Both the damaged intake boot and the faulty oil cap were replaced.
- The intake boot leak was large enough to possibly spot without the smoke machine, but the machine is very useful for finding smaller leaks and evaporative emission system problems.
A lean condition and check engine light on a BMW 750i can be caused by air leaks in the intake system. Common sources include a damaged intake air boot or a faulty oil cap. Since the crankcase is sealed to the intake system, any air leak - even at the oil cap - will cause a lean condition and trigger misfires.
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- BMW intake boot leak
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- New BMW 750i intake boot
This BMW came in with multiple cylinder misfires, we scanned the engine control computer and found errors for misfires and an error for a lean condition. Our BMW factory trained technician suspected an air leak in the intake system. He connected to intake system to our smoke machine to check for intake leaks. He found leaks at the main intake air boot and the oil cap. A modern German car can not have air leaks in the intake system or the crankcase, because the crankcase is a sealed to the intake system, an air leak at the oil cap will result in an air leak in the intake system and therefore a lean condition. In this case the primary leak that was causing both errors was from a badly damaged intake boot, but we replaced both defective parts. This leak was big enough we probably could have found it without the smoke machine, but the machine is invaluable for finding smaller intake leaks and evaporative emission system problems.