Most Likely Culprits:
* Mass Airflow Sensor (MAF) Problem: The MAF sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor will provide inaccurate readings, leading to poor fuel delivery and hesitation, especially at higher speeds. This is a common cause of this type of issue.
* Throttle Position Sensor (TPS) Issue: The TPS tells the computer the throttle's position. A faulty TPS can cause erratic fuel delivery and hesitation. Similar to the MAF, it's a frequent suspect.
* Catalytic Converter Issues: A clogged or failing catalytic converter can restrict exhaust flow, causing a lack of power, especially at higher RPMs (speeds). This is more likely if you also notice reduced power across the board, not just after 50 mph.
* Ignition System Problems: Worn spark plugs, failing ignition coil(s), or a damaged distributor cap/rotor (if equipped) can lead to misfires, causing hesitation and potentially illuminating the check engine light. This is more likely to cause hesitation at various speeds, not just after 50.
Less Likely (but possible):
* Fuel Pump or Filter: A weak fuel pump or clogged fuel filter might not deliver enough fuel at higher demands (higher speeds). However, this usually causes problems across the speed range.
* Transmission Issues: While less likely to cause hesitation *specifically* after 50 mph, transmission problems can certainly affect acceleration. This is more likely if the hesitation is accompanied by slipping or unusual noises from the transmission.
* Oxygen Sensor (O2 Sensor): A malfunctioning O2 sensor can affect the air/fuel mixture, but this often leads to broader performance issues.
What to do:
1. Get the Diagnostic Trouble Codes (DTCs): The most crucial step is to get the DTCs from the car's computer. This can be done using an OBD-II scanner (available at most auto parts stores). The codes will give you a much clearer indication of the specific problem.
2. Check the Obvious: Before jumping to expensive repairs, check simple things like:
* Engine air filter: A clogged filter restricts airflow.
* Fuel cap: A loose or damaged gas cap can trigger a code related to the evaporative emission system, which can cause performance issues.
3. Consult a Mechanic: Once you have the DTCs, you can either use online resources (with caution!) or consult a mechanic to diagnose and repair the problem. A mechanic will have the tools and expertise to properly assess the situation and fix it efficiently.
Don't attempt extensive repairs without knowing the underlying cause. The check engine light and hesitation are clear indicators that something is wrong, and ignoring it could lead to more significant damage or safety concerns.
