tell me why on 2003 Mitsubishi Montero Sport

I took my car to the shop on Saturday, I asked them to do my tune up & major service,they go to do the work and come tell me that there is oil where my spark plugs so i asked what does that mean, the guy say will im going to have to replace your valve cover gasket, so they do that and i go to get my car an i here this knocking sound im like what the heck ,the guy at the shop say now we have to replace your cadillac converter on the driver side...well in my mind im thinking my car was not sounding like that when i drop it off... Im so upset well.... my question is, Is it something they done or was it something that was about to happen?

by in Pittsburg, CA on February 13, 2012
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1 answer
ANSWER by , February 13, 2012
Oil leaking into the spark plug tubes is a common enough problem with lots of engines over time the seals fail, if the fail the plug tube seals fail oil will cause the ignition to short out and oil will damage the ignition coil or plug wire where applicable. Nothing they did would cause a cat converter to fail so quickly but usually if a cat converter is failing you get a P0420 code set/Check Engine-Service Engine Soon light to come on. But I hear cat converter rattle without setting a code as they about to fail.