Hello everyone, so my camaro is giving me a headache lately and I am just not sure what is going on with it. So I guess ill start with the most noticeable symptom, the exhaust rattle. The rattling is intermittent and occures around 1500 RPM and at low speeds but never when idoling.
Next, my check engine light is putting out the code P0420 (Catalyst System Efficiency Below Threshold (Bank 1)) which makes me think I just need a new Cat but im still not sure that would fix the rattling. Also, my exhaust has been dong a lot off decel popping which makes me think that im getting unburnt fuel in the exhaust system, which could have caused my Cat to go bad. That makes me leary to just go and put another Cat in and just have that one burn up a year later.
And to make things more interesting it appears that I am getting oil in my coolant. Im not sure if these symptoms are linked or not but I could use any help I can get. The best part about this enntire situation is that my car seems to be running great! The exhaust rattle is just becoming to loud that I would like to fix it. Thank you!

 

sure sounds like a plugged cat. the converter can rattle when it starts to go apart. the shield for the cat/exhaust is know to rattle so you may want to check to make sure its not up against anything that would let it rattle. plugged cat can cause engine to run rich which can foul 02 sensors and effect the readings they put out causing even more fuel to be sent to cylinders. remove or replace cat and replace fouled 02 sensors. when was the last time coolant was changed. old antifreeze can form a gunk that looks like oil. flush and put some new coolant in her.

 

I have it flush probably 2-3 times a year and the most recent one was about 3 weeks ago.

 

woh, can you post a picture, photobucket works good on this site. open free account, download pictures, copy img code to your post and it shows. very unusual for oil in the coolant.