CEL Code P0430 after intake manifold replacement

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12-02-2010, 12:31 PM

rmb2003

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Join Date: Dec 2010

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CEL Code P0430 after intake manifold replacement

I have a 2003 Ford Crown Vic with 146K miles on it. About 4 months ago the engine started occasionally misfiring so I decided it was probably time for a tune up. While changing the plugs I found some coolant in the #5 and #6 spark plug wells. There was not much so I cleaned out the coolant, changed the plugs and she ran fine. I was not able to find a leak so I stopped looking. About 3 weeks later she began misfiring again, this time the check engine light came on indicating misfire in #5 and #8. After pulling off the ignition coils I found significant amounts of coolant in all 4 driver side spark plug wells. I cleaned it up, replaced the coils and started her up in search of the coolant leak source. The leak was originating from the intake manifold near the thermostat housing. Damn! I was able to temporarily patch the leak, but I decided to replace the intake manifold this past weekend after the leak resurfaced. The replacement went well and the car once again runs great. However the check engine light came on a few days after the manifold replacement with a P0430 code (catalyst efficiency below threshold-bank 2). I retourqued the manifold bolts and checked for vacuum leaks in and around the plenum, throttle body, EGR valve, fuel injectors, and all along the intake but could not identify any vacuum leaks. I cleared the code and the car ran again for about 100 miles before the check engine light came on again. My initial reaction is that the code was directly related to the manifold replacement but now I think I may actually have a bad CAT or O2S, especially considering the severity of the misfires which prompted the manifold replacement to begin with. Has anyone had a similar experience in the past? Does it make sense that the CAT may have been faulty all along but did not trigger a DTC until the manifold was replaced? Thanks for the feedback.