1998 Ford Taurus Cylinder 6 Misfire: Check Engine Light & No Heat - How to Diagnose and Fix

For misfire issues in cylinder 6, start by inspecting the spark plug condition—check for wetness, color (black, tan, damaged), and proper firing. Verify that the fuel injector is pulsing using a noid light or test light. Fuel pressure should also be checked, especially if there's a leak or clogged injector. Premium fuel does not contain higher detergents than regular fuel—try adding one can of Sea Foam fuel treatment (available at Walmart) to the tank instead. Always perform a full diagnostic: read the #6 plug condition, conduct a fuel pressure test, and run a leak-down test with a gauge under KOEO conditions. Use a noid light to confirm that cylinder 6 is receiving proper injector pulse. This helps rule out electrical faults before moving on to more expensive repairs.

The 1998 Ford Taurus can have either a 3.0L Vulcan (standard V6) or a 3.0L DOHC (dual overhead cam) engine—these are mechanically different and require distinct diagnostics. To identify the engine type: if the spark plug is mounted on the side of the head, it's a Vulcan; if it goes through the center of the valve cover, it's a DOHC. Since you've replaced plugs, wires, and the coil pack, the next steps should include: 1. A compression test on cylinders 1–3 (front bank). Given the mileage, expect readings between 160–180 psi. If cylinder 6 shows significantly lower or higher pressure than others, inspect valve springs for breakage—this is a common failure in older Taurus engines. 2. To replace valve springs safely: use shop air to hold them closed during replacement, or insert nylon rope into the cylinder on compression stroke and slowly raise the piston by hand (never crank with starter). 3. Check power and ground circuits to injector #6 using a 12V test light with two probes. Disconnect the coil plug first to prevent spark. If the bulb flashes as the engine cranks, both voltage and current are present. 4. If no flash, check for broken wiring or grounding issues—verify power from battery (ground the test light to battery; if it lights when cranked, power is good). A faulty ground path will cause misfire. 5. If circuits are intact but no pulse, the PCM may be failing and needs replacement and reprogramming. 6. To test injector function: remove fuel rail bolts, secure injectors with zip ties, gently wiggle the rail while cranking. Disconnect injectors #4 and #5—crank for 2–3 seconds. If no spray occurs, replace the injector. Note: These steps apply primarily to DOHC engines. In Vulcan engines, a common issue is partial injector clogging leading to lean conditions, which can cause intake valve burnout and require head repair—a costly fix not recommended for DIYers.

If your Taurus has a distributor with a sensor (not a cap), the bearing may be failing and causing a chirping noise. This can trigger misfire signals in the fuel injection system. My suspicion is that the issue lies with the cylinder 6 injector—try unplugging it while the engine is running to see if the sound or behavior changes.

The misfire has now become intermittent—it turns on and off randomly. After retesting, the code still shows a misfire in cylinder 6. The issue appears to be stable and likely originates from the injector itself. Mechanical failures typically don’t go away like this, so I believe it's a faulty fuel injector in cylinder 6.

I'm having trouble starting the engine—it cranks continuously even when I turn off the key. The engine doesn't start and keeps running on crank. What could be causing this? This is a separate issue from the misfire but may relate to electrical system faults.

For continuous cranking without starting, check the starter relay—this is one of the most common causes of persistent cranking in older vehicles like the 1998 Taurus. A faulty relay can prevent proper engine start while allowing the starter to keep turning.