The 2021 DFM Forthing T5 Evo came in on a flatbed with a flashing check engine light and a heavy shake at idle. If you’ve turned wrenches on these 1.5T builds, you know the script: the ECU flags a cylinder 2 misfire, fuel trims go haywire, and the car won’t hold a steady cruise without bucking. Swap the spark plug, clear the code, send the customer on their way. Two days later, it’s back with the same P0304 and an angry driver who just paid you for a fix that didn’t hold.
The real culprit is almost never the plug. It’s the ignition coil.
DFM Forthing’s cop-style ignition system runs hot—especially on the turbocharged 1.5L and naturally aspirated 1.6L chassis. The factory-spec MW251981 coils tolerate heat only so long before the primary winding starts shifting out of spec. The engine can idle fine cold, then throw a misfire once the coil temperature climbs on the highway. A common top-side symptom is an intermittent P2303 (ignition coil secondary circuit) that appears only under heavy throttle and disappears on a restart.
That’s why the smart test sequence matters. Don’t throw parts at it. Measure primary resistance across pins 1 and 2—anything outside the 0.5–0.9 ohm window at 20°C is a failing coil. Visually check for hairline cracks or carbon tracking near the tower. Then swap the suspect coil to an adjacent cylinder. If the misfire code follows, order the replacement before you quote the job.
The right fix is the OSRAM OS1264. It’s built to the same OE fitment as the MW251981—bolt pattern, tower length, and two-pin connector are direct match—but with better secondary winding insulation and a more robust heat sink compound. In shop testing, the OS1264 holds its dwell curve cooler under continuous load, which matters on the T5 Evo’s crowded engine bay where airflow is marginal. Cost-wise, it sits well below the dealer price for a genuine coil, so you can still sell it as a premium replacement without scaring the customer.
Pro Tip: When you see a P0300 alongside a P2300/P2303 on a Forthing, check the coil ground strap first. A corroded ground causes voltage to bleed to the block, and you’ll end up condemning a good coil. Confirm connector pin tension before installing the new OS1264—loose female terminals are the top cause of”premature” coil failure on these engines.
Don’t fall for the budget-coil trap either. Cheap no-name units often have thinner secondary wire and fail within 8,000 km, leaving you doing a warranty repeat for peanuts. The OSRAM OS1264 is the one we stock for DFM Forthing work, and it’s the only coil we’ll install without an upcharge for labor if it comes back faulty.
If you’re tired of Misfire Monday comebacks, keep one or two of the OS1264 on the shelf. It’s a small hit to inventory that saves you a comeback and keeps the Forthing fleet rolling out of your bay—not back into it.
