When used with care, introducing propane into the intake system to enrich the A/F ratio is a quick and generally efficient method for diagnosing fuel density misfires. Practice makes perfect and collecting known-good data in your scan tool or scope memory for future reference is the best way of recognizing the various causes of an intermittent misfire. While space doesn’t allow a more detailed explanation of scan tool and scope diagnostics, keep in mind that many excellent training books and videos are available through several reputable aftermarket suppliers. In-cylinder pressure transducer testing is an excellent method for accurately testing running compression and camshaft timing. In this waveform, the exhaust valve opens at cursor 1, while the intake valve closes at cursor 2. Photo 4: While pressure transducer testing requires advanced labscope skills, it’s well worth learning to help diagnose compression and camshaft timing problems.
#Snap on modis ultra secondary ignition install#
Lastly, always install a long-life spark plug that meets the OE manufacturer’s standards for heat range, shell plating and electrode design.
Excess anti-seize compound can cause a misfire under load by spattering on spark plug electrodes. Manufacturers differ on whether or not to recommend the use of anti-seize, but most do not. Using an anti-seize compound is also an issue because the compound must be nickle-based. Many intermittent ignition misfires can be prevented by using a rubber spark plug holding tool to keep the insulators clean when installing new spark plugs. In most cases, the diagnostic tech must pursue intermittent ignition faults by visually inspecting parts for spark perforation or carbon tracking, or by using a labscope to monitor ignition activity. Since misfires caused by coolant leaking from cylinder head gaskets often depend upon engine temperature, they can become very intermittent. Some intermittent misfires can be more easily detected if a scan tool displays an individual cylinder misfire count in its datastream, or monitors coil activity and variations in burn time and primary coil amperage.
#Snap on modis ultra secondary ignition drivers#
Intermittent ignition misfires can be caused by faulty spark plugs, spark plug wires, ignition coils and ignition coil drivers located in the ECM. Photo 2: To prevent cylinder misfires at idle speed, some ignition systems fire each spark plug twice, producing a “double-strike” waveform.