* No fuel to that cylinder: The most obvious effect. That cylinder will not receive fuel, and therefore will not combust. This will lead to significantly reduced power.
* Rough running: The engine will run very roughly, potentially shaking violently. The imbalance caused by one cylinder not firing will be noticeable.
* Increased emissions: The unburnt fuel will be expelled through the exhaust, resulting in increased hydrocarbon (HC) and potentially particulate matter (PM) emissions. This could trigger a check engine light.
* Potential for damage (long-term): While unlikely in the short-term, continuously running with a dead cylinder can cause issues. The uneven firing can create increased stress on other engine components. The lack of combustion in that cylinder could contribute to overheating in the long run. In a diesel, the lack of lubrication from fuel combustion can also exacerbate cylinder wear.
* Diagnostic challenges: While unplugging an injector helps confirm a faulty injector as the source of the dead cylinder, it might mask other problems. For example, a fuel delivery issue to all injectors might be misinterpreted if focusing solely on the disconnected injector.
In short: Unplugging a fuel injector on a dead cylinder is a diagnostic step, not a solution. It helps to isolate the problem but doesn't fix it. The underlying cause of the dead cylinder (faulty injector, low fuel pressure, electrical issue, etc.) still needs to be identified and repaired. Running the engine for extended periods with a fuel injector unplugged is strongly discouraged.
