# cps or plugged cat



## whojohnjones (Aug 2, 2011)

my 2002 2.5 altima gas started running a little rough in lower rpms and at idle and doesn't want to go past 4k at 60mph please help me


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## techtalk (Jun 8, 2011)

whojohnjones said:


> my 2002 2.5 altima gas started running a little rough in lower rpms and at idle and doesn't want to go past 4k at 60mph please help me


Hello John,

Here are the symptoms of a clogged cat:

Loss in power/acceleration- When a converter becomes clogged with debris or are broken, the engine has to work much harder to accelerate and idle because the exhaust pressure is backing up in the pipe. This causes a highly erratic idle and or stalling and little or no power on acceleration, as well as higher engine temperatures. If your vehicle suddenly seems to lose more than half its power, the catalytic converter could be the culprit.

Bad fuel mileage- A clogged catalytic converter makes the engine work much harder, therefore gas mileage can decrease substantially.

Rattling sound upon acceleration- Sometimes the honeycomb-like structure inside of your cat that aids the converter in superheating the exhaust fumes breaks down over time. This may cause pieces to break off and rattle around inside your cat. Do you hear a rattling sound originating from the exhaust/cat whenever you accelerate? 

Wait until your car is COMPLETELY cooled off and shake your catalytic converter around in order to replicate a rattling sound. 

Your catalytic converter could still be bad even if it doesn't exhibit all of the aforementioned symptoms. A back pressure test can also help determine whether or not the cat is clogged.



Hope this helps!


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