* Fuel Pump or Fuel Filter: The fuel pump might be weakening with age, unable to supply enough fuel at higher RPMs when the engine demands more. A clogged fuel filter would have a similar effect. This is a common cause of power loss under load.
* Fuel Injectors: One or more fuel injectors could be clogged, sticking, or failing to deliver fuel properly at higher RPM. This would lead to a lean condition (not enough fuel) and cause the engine to cut out.
* Ignition System: Problems in the ignition system, such as:
* Worn spark plugs or wires: These can misfire under higher engine loads.
* Ignition coil: A failing ignition coil may not be able to provide sufficient spark at higher RPM.
* Distributor cap and rotor (if applicable): Cracks or wear in these components can interrupt the spark delivery. The 1996 626 might or might not have a distributor depending on the exact engine. Look up your specific engine code to be sure.
* Crankshaft Position Sensor (CKP sensor): This sensor tells the engine's computer the position of the crankshaft. A faulty sensor can cause misfires and power loss.
* Mass Airflow Sensor (MAF Sensor): This sensor measures the amount of air entering the engine. A faulty MAF sensor can provide inaccurate readings, leading to a lean fuel condition and engine cut-out.
* Throttle Position Sensor (TPS): An inaccurate reading from the TPS can cause the engine computer to miscalculate fuel delivery.
* Engine Control Module (ECM): Though less likely, a failing ECM could be the culprit. This is usually diagnosed last after other components have been checked.
* Vacuum Leaks: A significant vacuum leak can disrupt air/fuel mixture, especially noticeable at higher RPMs.
Troubleshooting Steps:
1. Check the obvious first: Start with the easiest and cheapest checks. Inspect spark plugs and wires for wear. Check the fuel filter for blockages (it's usually easily accessible).
2. Listen for unusual noises: Does the fuel pump make a whining noise? Are there any unusual clicking or ticking sounds from the engine?
3. Check engine codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored by the engine's computer. This can provide valuable clues.
4. Test fuel pressure: A fuel pressure gauge can measure the fuel pressure at the fuel rail. Low pressure at higher RPMs points to a fuel pump or filter problem.
5. Professional diagnosis: If you're not comfortable working on your car, take it to a qualified mechanic for proper diagnosis and repair. They have the tools and expertise to identify the root cause more efficiently.
The 3500-4000 RPM range suggests a problem that only surfaces under load, making fuel delivery and ignition the prime suspects. Systematic checking of the components listed above is the best approach to finding the solution. Remember safety first when working on your vehicle.
