Experiencing engine trouble can be frustrating, and recently, I faced an issue that had me scratching my head. While I didn’t have access to a scope, I started my diagnostic process with a timing light on the number one cylinder wire while driving. I had come across threads suggesting injectors as a potential culprit for the problems I was observing, but the timing light test pointed towards an ignition issue, specifically a cylinder misfire on cylinder 1. The timing light would fail to flash when the car began to stumble, clearly indicating an ignition cut-out. Even when the engine seemed to run smoothly, the timing light flash appeared inconsistent.
Suspecting a faulty ignition coil, I decided to swap out the aftermarket coil with a known good OEM (Original Equipment Manufacturer) coil. Immediately, the car’s performance improved significantly, especially for a while. However, the idle still felt weak and unstable, suggesting there might be more to the problem than just the coil, potentially still hinting at cylinder 1 misfire related issues affecting the idle.
To address the weak idle, I explored another online forum suggestion: resetting the ECM (Engine Control Module) idle parameters. This procedure involved disconnecting the battery for 30 minutes, reconnecting it, turning the ignition key to the ‘on’ position for 20 seconds, and then starting the engine and letting it idle for 20 minutes. Unfortunately, this attempt failed as the car refused to idle correctly and would die after approximately five minutes. This persistent idle issue further suggested an underlying problem beyond just ECM settings, possibly still related to Cylinder Misfire 1 or factors exacerbating its symptoms.
Continuing my search for a solution, I found another helpful thread discussing throttle body cleaning. The theory was that carbon buildup or “gunk” around the throttle blade could prevent it from closing fully, disrupting the idle. Following this advice, I removed the throttle body and, to my surprise, it was indeed heavily contaminated with gunk inside. Using solvent and a soft brush, I thoroughly cleaned the throttle body, paying special attention to the throttle blade face and edges, as well as the throttle body bore. After cleaning and reinstalling the throttle body, I was finally able to successfully reset the ECM idle parameters. This time, the car idled perfectly for the full 20 minutes of the reset procedure. I then shut it off for a minute, turned the ignition back on for 20 seconds without starting the engine, and restarted it. The engine ran well, and the idle was stable for at least five minutes, indicating a successful resolution. The ECM was now properly controlling the idle, and the potential cylinder misfire 1 symptoms at idle seemed to be resolved.
Reflecting on the repair, it became clear that the issue with the throttle body wasn’t necessarily the blade being unable to close completely. Instead, the gunk accumulation around the bore perimeter and blade edge was likely blocking the very narrow gap between the blade and the bore when closed. This minute gap is crucial for allowing just enough air to pass for a stable idle. Without this precisely controlled airflow, the idle becomes erratic and unstable, potentially mimicking or exacerbating symptoms of cylinder misfire 1, especially at low RPMs.
With the throttle body cleaned and the OEM coil installed, the engine is running smoothly. It appears the non-OEM aftermarket coil was indeed a contributing factor to the initial ignition issue, potentially causing cylinder misfire 1. However, the non-OEM plug wires and spark plugs seem to be functioning correctly and were not part of the problem in this case.
If the engine trouble, particularly any recurrence of symptoms suggestive of cylinder misfire 1 or idle instability, returns, I will provide an update. Thank you to the online community for the valuable suggestions that guided this troubleshooting process.
