1999-2004 Tracker & 1999 Sunrunner Ignition Coil Failure: Misfires, Diagnosis, and Replacement

Vehicle and Engine Compatibility

This ignition coil is a direct replacement for the 3-pin connector coil-on-plug units used on the following vehicles:

• 1999-2004 Chevrolet Tracker (with 2.0L 4-cylinder or 2.5L V6 engines)
• 1999 Pontiac Sunrunner (with 2.0L 4-cylinder engine)

Symptoms of a Failing Ignition Coil

When an ignition coil starts to fail, it can't deliver a consistent, high-energy spark. This leads to a variety of noticeable engine performance problems. Here are the most common signs:

• Check Engine Light: This is often the first sign. A failing coil will cause an engine misfire, which the vehicle's computer will detect and log as a trouble code. Common codes include P0300 (Random/Multiple Cylinder Misfire) or specific cylinder misfire codes like P0301, P0302, P0303, etc. You may also see codes specifically for the coil circuit, such as P0351.
• Engine Misfire (Rough Running): This is the most distinct symptom. A misfire feels like a stumble, shudder, or jerking from the engine. It can be most obvious when idling (feeling like a rough, vibrating idle) or when accelerating under load, like going up a hill.
• Reduced Power and Poor Acceleration: With one cylinder not contributing its full power, the vehicle will feel sluggish and weak.
• Difficulty Starting: The engine may take longer than usual to crank and start, or it may start with a rough, sputtering sound. In a no-start situation, it's unlikely that a single bad coil is the sole cause, as the engine should still be able to run on the remaining cylinders.
• Worse Fuel Economy: When a cylinder misfires, unburned fuel is wasted and sent out the exhaust. The engine's computer may try to compensate, leading to a noticeable drop in MPG.
• Gasoline Smell or Black Smoke: A strong smell of raw gasoline from the exhaust is a sign of unburned fuel passing through the engine, which can be caused by a dead coil. This can quickly damage the expensive catalytic converter.

Known Issues, TSBs, and Recalls

Searches of the National Highway Traffic Safety Administration (NHTSA) database show no specific recalls or Technical Service Bulletins (TSBs) for ignition coil failure on the 1999-2004 Chevrolet Tracker or 1999 Pontiac Sunrunner. While GM had major recalls for ignition *switches* in other models around this time, those issues do not apply to this part or vehicle. The most significant recall-level issue for these Trackers involves severe rust and corrosion of the front suspension crossmember, particularly in salt-belt states.

Diagnosing a Bad Ignition Coil

Pinpointing a bad coil on these engines is a straightforward process. Since the engine has individual coils, the goal is to identify which cylinder is misfiring and confirm if the coil is the cause.

1. Read the Trouble Codes: Use an OBD-II scanner to check for codes. A code like "P0302" points directly to a misfire on Cylinder #2. This tells you exactly where to start looking.
2. Swap the Coil: This is the easiest and most definitive test. Let's say you have a P0302 code. Unplug and unbolt the ignition coil from cylinder #2. Do the same for a known good cylinder, like cylinder #3. Swap their positions: install the coil from #2 onto cylinder #3, and the coil from #3 onto cylinder #2. Clear the codes with your scanner and drive the vehicle until the check engine light returns. If the new code is "P0303", you've confirmed the coil is bad because the misfire followed the coil to its new location.
3. Visual Inspection: When you remove the coil, inspect it for any obvious signs of failure. Look for fine cracks in the plastic housing, white or burnt-looking marks (carbon tracking), or corrosion on the electrical connector pins. Also check for oil inside the spark plug tube; a leaking valve cover gasket can cause oil to pool and destroy the ignition coil boot, leading to failure.
4. Test for Spark: Using an in-line spark tester is a safe way to see if the coil is producing a spark. The tool connects between the coil and the spark plug and will light up if a spark is present. A weak or intermittent spark indicates a failing coil.

Buying a Used Ignition Coil

Given that new OEM coils from GM are discontinued, a quality used OEM coil is an excellent choice and often superior to a cheap aftermarket alternative. Here’s what to look for when buying a used part:

• Physical Inspection: Closely examine the coil's plastic housing for any cracks, even hairline ones. Check the rubber boot for tears, swelling, or brittleness. Ensure the 3-pin electrical connector is intact and the pins are straight and free of corrosion.
• Verify Part Numbers: Match the part number on the coil to one of the known OEM numbers (e.g., 91175339, 33410-77E21) to ensure compatibility. While other coils may look similar, internal differences can cause performance issues.
• Ask About the Source Vehicle: If possible, find out the mileage of the vehicle the part came from. Coils are a wear item, but a part from a lower-mileage vehicle is likely to have more life left in it.
• Why Used OEM is a Good Choice: Original Equipment (OEM) coils made by the vehicle's manufacturer (or their supplier, like Delphi) were built to a higher quality standard than many low-cost aftermarket parts. They use better materials for the internal windings and outer housing, making them more resistant to heat and vibration, which translates to better reliability and longevity.

Replacement Guide (DIY Difficulty: 1/5)

Replacing an ignition coil on the Tracker's 2.0L or 2.5L engine is one of the easiest repairs you can perform. It requires only basic hand tools and takes just a few minutes per coil.

1. Locate the Coils: Open the hood. The ignition coils are mounted directly on top of the engine's valve cover, one for each cylinder.
2. Disconnect the Connector: Press the release tab on the electrical connector and pull it straight off the coil. Be gentle, as old plastic can be brittle.
3. Remove the Hold-Down Bolt: Each coil is secured by a single 8mm bolt. Use an 8mm socket to remove it.
4. Remove the Coil: Gently twist the coil back and forth while pulling upwards to release the boot's seal from the spark plug. If the boot is stuck, do not yank on it, as it may tear and leave the bottom half in the spark plug well. If this happens, you may need to use needle-nose pliers to retrieve the pieces.
5. Install the New Coil: Apply a small amount of dielectric grease to the inside of the new coil's boot. This helps seal out moisture and makes future removal easier. Press the new coil firmly down onto the spark plug until it seats. Reinstall the 8mm bolt (do not overtighten) and reconnect the electrical connector until it clicks.

Cost of Replacement

The cost to replace an ignition coil varies depending on the part source and whether you do the work yourself.

Frequently Asked Questions (FAQ)