compression Posted December 18, 2013 Posted December 18, 2013 All stock 2.5i, manual transmission. 81k miles. Very well taken care of. Last week while cruising on freeway, CEL went on. Happened to have my OBDII scanner in my glove box by coincidence. So, while driving, I scanned the code P0420 -catalytic low efficiency, then cleared it. Week later, another code comes on just after starting, P1518 - starter switch circuit low input. Once again, cleared it and continued on. Ever since, my idle has been low. When settling into idle after revving the engine, it drops down to 300-400RPM stumbles a little, then bounces back up to 800 RPM. Some times it stays at 500RPM and stumbles. During driving/accelerating/decelerating/etc the car feels fine. Are all of these symptoms related? P1518 could be the result of the cold weather we are having and the fact the battery is old and probably near end-of-life, resulting in "too low" voltage during cranking or something. Just odd all of this shit happens at the same time after years of trouble free running. Any input greatly appreciated. Thanks
LongHiway Posted December 18, 2013 Posted December 18, 2013 Dunno for sure. My cat failed last summer (w/ a CEL that would come on, then go off for a few days). The car ran fine, even at idle. Here in MA, there's an extended warranty for selling a "low" emission car so, the repair was free, even a loaner car. Maybe Oregon is similar to MA when selling a low emission car?
ehsnils Posted December 18, 2013 Posted December 18, 2013 Manifold donut gaskets. They shrink, especially when it gets cold. If they haven't been replaced before they are the prime suspect for a bad idle.
Leviman Posted December 18, 2013 Posted December 18, 2013 Sounds to me like your computer forgot it's idle settings. My car will do that after disconnecting the battery.
compression Posted December 19, 2013 Author Posted December 19, 2013 Interesting points everyone. Keep it coming. Thanks.
compression Posted January 2, 2014 Author Posted January 2, 2014 well, problems went away and have not come back. so I guess I will blame these on tiny unicorns living in my exhaust pipe and poking holes in it.
compression Posted January 13, 2014 Author Posted January 13, 2014 P0420 popped back up. Going to have to start the long process of diagnosis to figure out why the catalytic converter is not lighting off. Its funny, but when the P0420 comes on, and I clear it, the car idles like shit for a couple days.
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