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Failed Emissions CulpritsThis information was copied out of the Honda OBD training manual. Submitted by: Jaime 91sib18 on the 4th-Gen-Civic.com ForumFailed the CO! Check the fuel pressure and regulator along with Ignition Timing. Over advancing the timing will cause high CO readings. When setting ignition timing, fuel pressure, and idle speed, follow the book. Make sure and jump the connector for setting the timing, resisting the temptation to "advance" it for performance during this time. Also make sure the vacuum line(s) all have good fitmit, along with no cracks, cuts, ect... exspecially going to the MAP Sensor. Check the O2 sensor system to ensure it is working properly and has not been damaged/contaminated. Also check the oil, diluted oil will also cause high CO readings. Worn rings and valve guides will contribute to this also. However this will only be a problem on very tired engines. Failed the HC! Check the ignition system first, this usually caused by an ignition miss. Anywhere from a failing coil, igniter, spark plug(s) for fouling/fouled, spark plug wires due to age. Then check the engine for poorly seated valves, leaking head gaskets, or other compression problems, will put the HC readings through the roof. A "Leak Down Test" will have to be performed, a Compression Test will not work this case... Also check for vacuum leaks and the injector spray patterns. Remember, HC failures are usually caused by compression or ignition problems. Improper fuel distribution/vacuum leaks will cause misfires that will cause excessive HC. Failed both CO and HC! If the HC is very high and the CO is close, you probably have an ignition/compression related problem. If the CO is very high and the HC is close, than you may only have a timing/fuel pressure problem. |
