* Fuel Delivery Issues:
* Fuel Pump: The pump might be weak. It can supply enough fuel at idle, but struggles to keep up with the increased demand when you accelerate. A failing fuel pump often exhibits symptoms like hesitation or bogging down under acceleration.
* Fuel Filter: A clogged fuel filter restricts fuel flow. Similar to a weak pump, this will show up more prominently under load.
* Fuel Injectors: A clogged or malfunctioning injector(s) might not be delivering enough fuel at higher RPMs. This could be due to dirty fuel, worn injectors, or electrical problems.
* Fuel Pressure Regulator: This component regulates fuel pressure within the system. A faulty regulator could lead to inconsistent fuel pressure, causing issues under load.
* Ignition System Problems:
* Spark Plugs/Wires: Worn or fouled spark plugs can cause misfires, especially under higher engine loads. Similarly, damaged spark plug wires can prevent a strong spark from reaching the plugs.
* Ignition Coil: The coil provides the high voltage for the spark plugs. A faulty coil can lead to misfires or complete lack of spark in one or more cylinders.
* Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP): These sensors tell the engine's computer the position of the crankshaft and camshaft. If these sensors are malfunctioning, the timing of the spark and fuel injection can be off, leading to poor performance, especially under load.
* Air Intake System:
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor provides inaccurate air flow readings to the engine's computer, leading to incorrect fuel delivery.
* Air Filter: A severely clogged air filter restricts airflow, causing similar problems to a MAF sensor issue. While less likely to cause this specific symptom alone, it's worth checking.
* Other Possibilities:
* Transmission Issues (if automatic): While less likely given the description, a problem within the automatic transmission could cause it to not engage properly under load.
* Exhaust Restriction: A severely clogged catalytic converter or muffler could restrict exhaust flow, impacting engine performance.
Troubleshooting Steps:
1. Check the Easy Stuff First: Start with the easiest and cheapest things to check:
* Air Filter: Replace if dirty.
* Spark Plugs: Inspect for wear and fouling. Replace if necessary.
2. Diagnostics: A scan tool (OBD-II reader) can retrieve diagnostic trouble codes (DTCs) from the engine control unit (ECU). This can help pinpoint the problem. Auto parts stores often offer free code reading services.
3. Professional Help: If you're not comfortable working on your car, take it to a mechanic. They have the tools and expertise to diagnose the issue accurately and efficiently. Describing the symptoms precisely—that it runs fine at idle but bogs down under load—will be crucial for them.
Don't continue driving the car extensively with this problem, as you risk further damage. The underlying cause needs to be addressed as soon as possible.
