Here's a breakdown of the possibilities:
* Faulty Fuel Injector: The most probable cause. The injector might be intermittently clogged, sticking open or closed, or have a failing internal component.
* Wiring Issues: A problem in the wiring harness to that specific injector is a strong possibility. This could be:
* Loose connection: Check the connector at both the injector and the engine harness. Corrosion or a loose pin is common.
* Damaged wire: Look for cuts, abrasions, or chafing in the wiring leading to the injector.
* Short circuit: A short could cause the injector to malfunction intermittently.
* Faulty ECM signal: While less likely given the swap test, a problem with the Engine Control Module (ECM) sending the correct signal to that specific injector is possible.
* Fuel Pressure Issues (less likely): While swapping injectors points away from this, consistently low fuel pressure *could* manifest in similar symptoms. If the fuel pressure is marginal, a slightly weak injector might struggle. This needs to be checked with a fuel pressure gauge.
Troubleshooting Steps:
1. Inspect the Injector Connector: Carefully examine the connector for corrosion, bent pins, or loose connections. Clean any corrosion with electrical contact cleaner. Try reseating the connector firmly.
2. Visual Inspection of Wiring: Carefully trace the wiring harness from the injector back to the ECM. Look for any obvious damage to the wires.
3. Check for continuity (advanced): Use a multimeter to check the continuity of the injector wiring. You'll need a wiring diagram to identify the correct wires.
4. Fuel Pressure Test (advanced): If the above steps don't reveal the problem, a fuel pressure test can help rule out low fuel pressure. This typically requires a specialized gauge.
5. Injector Flow Test (advanced): This requires a specialized injector testing tool, but would definitively test if the injector is faulty.
In summary: Start with the simplest checks (connector and wiring inspection), then move to more advanced diagnostics if necessary. Since the problem seems tied to a specific injector, focus your efforts there. A faulty injector is the most likely culprit.
