Fiat Petra rough running stalling

Greetings! I had a similar experience with my Petra, though I can't recall the exact year model. Your symptoms—rough running, stalling, CEL, and jerking—strongly suggest a misfire, and the ignition coil is indeed a prime suspect. Before condemning the coil itself, meticulously inspect the cable and plug connections. A loose or corroded connection can mimic a failing coil. Have you performed any vehicle diagnostics to pinpoint the cylinder?

Thanks for the tip! I haven't done any in-depth diagnostics yet, just a visual check of the wiring. By 'vehicle diagnostics,' do you mean using an OBD2 scanner to read the error codes? And how can I pinpoint the cylinder?

Affirmative. Utilize an OBD2 scanner to extract the Diagnostic Trouble Codes (DTCs). A code such as P0301, P0302, P0303, or P0304 would indicate a misfire in cylinder 1, 2, 3, or 4 respectively. Furthermore, P0300 signifies a random misfire. Once you identify the affected cylinder, you can then focus your attention on the corresponding ignition coil, its wiring harness, and spark plug. However, given the symptoms, I strongly recommend professional diagnosis and repair. Coil failures can sometimes cascade into other issues if not addressed swiftly.

Thanks a lot for the detailed explanation and advice! I took it to a local mechanic. Turns out it was indeed a defective ignition coil, just like we suspected, and a corroded connector. They replaced the coil and cleaned up the connection, and it cost me around 95€. Runs like new now!