Fixing 1998 Subaru Forester Ignition Coil Problems

If your 1998 Subaru Forester is struggling to start, sputtering or throwing a misfire code, one of the most common culprits is the ignition coil. These units convert the battery’s low voltage into the high voltage needed to spark the spark plugs. Over time, especially in older engines, they can degrade and cause a cascade of performance issues.

Common Symptoms of 1998 Subaru Forester Ignition Coil Issues

When the ignition coils are on the verge of failure, you’ll notice several tell‑tale signs:

• Engine misfires – the car may shake, especially at idle or when accelerating.
• Difficulty starting – the engine may turn over slowly or require multiple attempts.
• Check Engine Light (CEL) – codes such as P0300 (random misfire) or P0301–P0304 (specific cylinder misfire) often point to coil problems.
• Reduced power and fuel economy – a failing coil can cause the engine to work harder and consume more gas.
• Excessive spark plug fouling – worn coils can deliver uneven spark, leading to spark plug deposits.

If you notice any of these symptoms, it’s time to inspect the ignition system.

Diagnosing the Problem: How to Check the Ignition Coils

Before replacing anything, you should confirm that the coils are indeed the source of trouble. Here’s a simple diagnostic flow:

1. Scan for codes – A quick OBD‑II scan will reveal misfire codes. If they persist after a start‑up, the coil is likely involved.
2. Visual inspection – Look for cracked or frayed wiring, loose connections, or signs of overheating on the coils.
3. Swap coils – Many Foresters have coil packs that feed two cylinders each. By swapping the packs between the front and rear, you can see if the misfire moves with the pack, confirming a coil issue.
4. Resistance test – Using a multimeter, measure the coil's primary and secondary resistance. Compare to Subaru’s spec sheet (typically 3–5 Ω primary, 5–10 kΩ secondary). Significant deviation indicates a bad coil.

If the diagnosis points to a coil, you’re ready to replace it.

Choosing the Right Replacement Coil for a 1998 Subaru Forester

Subaru’s 1998 Forester uses a 2‑coil, 2‑pack design: each pack serves two cylinders. When picking a replacement, you have two options:

• OEM (Original Equipment Manufacturer) – These are the exact parts Subaru used, guaranteeing compatibility and durability.
• Aftermarket equivalents – Reputable brands often match or exceed OEM specs, and they can be more affordable.

Key specs to match:

• Coil type – 2‑coil, 2‑pack (2‑coil/2‑pack).
• Output voltage – Around 20,000 V for a 2.5 L engine.
• Mounting style – Most coils attach with the same bracket and bolts, but double‑check the fit.

When in doubt, consult the 1998 Forester service manual or a Subaru‑specialized dealer.

Step‑by‑Step Replacement Procedure

Replacing the ignition coils on a 1998 Forester is a fairly straightforward job that can be completed in about an hour with basic tools. Follow these steps:

1. Prepare the Vehicle

• Disconnect the battery to avoid electrical shock.
• Raise the front of the car with a jack and secure it with jack stands.

2. Remove the Old Coil Pack

• Locate the coil pack on the engine block; it sits directly above the spark plug wires.
• Unplug the electrical connector (press the tab and pull gently).
• Unscrew the mounting bolt with a socket wrench.
• Gently lift the pack out. Be careful not to damage the spark plug wires.

3. Install the New Coil Pack

• Position the new pack, aligning the mounting holes.
• Secure it with the bolt, tightening to the torque spec (about 8 ft‑lb).
• Reconnect the electrical plug, ensuring a snug fit.

4. Final Checks

• Re‑connect the battery.
• Start the engine and look for smooth operation.
• Run a quick scan to confirm the CEL has cleared.

Repeat the process for the second pack if needed.

Tips to Extend Ignition Coil Life

While coils can be replaced, preventing premature failure can save time and money:

• Use high‑quality gasoline – Contaminants can damage coils.
• Keep spark plugs clean – Deposits can increase load on the coils.
• Check for vacuum leaks – Leaks can cause misfires that strain the coils.
• Avoid short idling periods – Cold, idling engines are more likely to generate excess heat on coils.

Regular maintenance keeps your Forester running smoothly.

When to Call a Professional

If you’re not comfortable working under the hood, or if the misfire persists after coil replacement, it’s wise to consult a mechanic. Persistent issues may indicate deeper problems such as faulty spark plugs, wiring harness damage, or ECU malfunctions.

FAQ

• What’s the life expectancy of an ignition coil on a 1998 Subaru Forester? Typically 80,000–100,000 miles, but can vary with driving conditions and maintenance.
• Can a bad spark plug mimic a coil failure? Yes; a fouled or worn spark plug can cause misfires that resemble coil problems.
• Is it safe to drive with a failing coil? Driving can be risky; misfires can cause loss of power and increase exhaust emissions.
• Do aftermarket coils perform as well as OEM? When sourced from reputable manufacturers, they often meet or exceed OEM standards.

By understanding the signs, diagnosing accurately, and replacing with the right parts, you can restore your 1998 Subaru Forester’s reliability and keep the engine running like new.