* Dirty or clogged fuel filter: This is a very common cause. A clogged filter restricts fuel flow, especially when the engine is demanding more (acceleration) or the fuel pump is working under pressure (idle). This is a cheap and easy part to replace first.
* Failing fuel pump: A weak fuel pump might provide enough fuel for low-demand situations (initial idle) but struggles when more fuel is needed. This manifests as sputtering under load. You might also hear a buzzing or whining sound from the fuel pump area (usually near the fuel tank) if it's failing.
* Clogged fuel injectors: Clogged injectors can't deliver a consistent spray of fuel, leading to rough running, sputtering, and stalling. Cleaning them (with a fuel injector cleaner added to the gas tank, or professional cleaning) might resolve the issue, but replacement may be necessary if they're badly worn.
* Vacuum leaks: Vacuum leaks disrupt the proper air/fuel mixture. This can cause all sorts of running problems, including the symptoms you describe. A visual inspection of all vacuum hoses is crucial. Look for cracks, holes, or loose connections.
* Ignition system problems: This could include:
* Worn spark plug wires: High-resistance wires can cause misfires, leading to sputtering and hesitation.
* Failing distributor cap or rotor: Similar to spark plug wires, these components can degrade over time, hindering spark delivery.
* Weak spark plugs: Old or fouled spark plugs can't ignite the air/fuel mixture properly.
* Throttle position sensor (TPS): A faulty TPS can provide inaccurate information to the engine control unit (ECU), resulting in incorrect fuel/air mixtures.
* Mass airflow sensor (MAF): Similar to the TPS, a bad MAF sensor can give the ECU faulty readings, leading to poor running. (Note that the '89 Tempo might not have a MAF sensor, depending on the exact engine; it's more common on later models).
* Idle air control valve (IAC): This valve regulates air flow at idle. A malfunctioning IAC valve could cause erratic idle speed and stalling.
Troubleshooting steps:
1. Check the easy things first: Start with the fuel filter. It's inexpensive and relatively easy to replace. Check your spark plugs and wires visually for obvious damage.
2. Listen for unusual noises: Listen carefully for unusual noises coming from the fuel pump area.
3. Visual inspection: Inspect all vacuum hoses for cracks, leaks, or loose connections.
4. Professional diagnosis: If you're not comfortable with mechanical work, take your car to a mechanic. They can use diagnostic tools to pinpoint the problem more accurately.
This is not an exhaustive list, but it covers the most likely causes. The fact that it sputters under load and almost stalls when stopping strongly suggests a fuel delivery issue, so start there. Remember to replace parts only after careful identification and verification.
