Ignition System:
* Worn spark plugs and wires: These are the most common culprits. Old, worn plugs misfire, causing a skip. Worn wires can't effectively transmit the spark. Replacing them is relatively inexpensive and easy.
* Distributor cap and rotor: Cracks or corrosion in the distributor cap and worn rotor can disrupt the spark delivery. Inspection and replacement are often necessary.
* Ignition coil: A failing ignition coil won't produce a strong enough spark. This needs testing with a multimeter or replacement.
* Ignition module (or control module): This component controls the ignition timing. A faulty module can cause misfires. This is more complex to diagnose and replace.
* Cranking Sensor: A bad sensor could cause intermittent problems with the spark timing.
Fuel System:
* Fuel filter: A clogged fuel filter restricts fuel flow, leading to hesitation and skipping. Replacing it is a relatively simple and inexpensive fix.
* Fuel pump: A weak or failing fuel pump might not supply enough fuel under acceleration. You might hear a buzzing sound when the key is turned on if the pump is failing. This is more difficult to diagnose and replace.
* Fuel injectors: Clogged or faulty fuel injectors can cause a misfire in individual cylinders. This requires specialized tools and knowledge to diagnose and clean or replace.
* Fuel pressure regulator: A faulty regulator can cause incorrect fuel pressure, leading to inconsistent fuel delivery.
Other Potential Causes:
* Vacuum leaks: Leaks in the vacuum system can disrupt engine timing and fuel delivery. Inspecting all vacuum lines for cracks or loose connections is crucial.
* Throttle position sensor (TPS): A faulty TPS sends incorrect information to the computer, affecting fuel delivery.
* Mass airflow sensor (MAF): This sensor measures the air entering the engine. A faulty MAF sensor can lead to a lean or rich fuel mixture, causing misfires.
* Engine sensors (O2 sensor, etc.): Several sensors monitor engine performance. A faulty sensor can cause the computer to send incorrect signals, resulting in skipping.
* Timing belt/chain: While less likely to cause a skip only under acceleration, a slipping or worn timing belt/chain can disrupt engine timing, leading to performance issues.
Troubleshooting Steps:
1. Start with the basics: Check the spark plugs, wires, distributor cap, and rotor. These are the easiest and cheapest components to inspect and replace.
2. Listen for unusual sounds: Pay attention to any unusual noises coming from the engine, like a buzzing fuel pump or ticking from the ignition system.
3. Check the fuel filter: This is a relatively simple and inexpensive check.
4. Use a code reader (OBD-I): While a 1990 Ranger likely doesn't have a standard OBDII port, you might find a code reader compatible with its system. This can help pinpoint specific sensor issues.
5. Consult a mechanic: If you're not comfortable troubleshooting the system yourself, a qualified mechanic can diagnose the problem accurately and efficiently.
Remember, safety first! Always work in a well-ventilated area when working on your vehicle. If you're unsure about any repair, consult a professional.
