Rattle When Accelerating: catalytic converter

Nguyen916

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4cyl. automatic. everything stock under the hood. i use to get 380 on a tank. now im getting 300 if im lucky. Car is slow to accelerate. Hard to drive up hills.

dude same here mine just started rattling for like 3 weeks and its getting really annoying, i needa fix this **** asap!
 

lltradell

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Here is a little update on day 1 - So after i took the honeycomb out of my rattling Cat, i reved the car in neutral and it stopped at 5K still. before i would drive my car maxed out at 5k (driving or neutral). After the cleaning, my car actully hit 6k in first gear. But in neutral, it stayed at 5k. Then i read that hondas in neutral will not rev over 5k. So this is a good sign. But i wont be able to get a MPG read for a week of driving or so. I really hope i fixed it cuz im contemplating on selling my car if i keep getting 19mpg.
 

lltradell

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The rattling was due to the loose honeycomb filter in the cat. I broke it up and took it out. So now my o2 sensor isnt getting filtered exhaust but i did the nonfouler trick and hopefully i dont get a code. If i do, i have no choice but to buy a new Cat.
 

001Stunna

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http://www.k-series.com/forum/showthread.php?t=8833
its only for code P0420, which i think means your Cat is bad. With the nonfouler trick, it limits exhaust to get to the o2 sensor.
And if cat is rattling, your gonna get the p0420 code. And when you get this code, your MPG is gonna go to s#it.

P0420 is a code for catalytic converter performing under threshold code

The catalytic converter has an oxygen sensor in front and behind it, upstream and downstream. When the car is warm and in operating temperatures it runs in closed loop, and hence looks at data from the o2 sensors on how to behave. The upstream oxygen sensor reading should fluctuate from around 0.2-0.8v. If it stays up or down for long periods of time it could indicate a faulty sensor. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This would mean that the cat converter isn't doing what its meant to do and not behaving up to ECU specs.

A code P0420 may mean that one or more of the following has happened:
-Leaded fuel was used where unleaded was called for
-An oxygen sensor is not reading (functioning) properly
-The engine coolant temperature sensor is not working properly
-Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
-Retarded spark timing
-The oxygen sensors in front and behind the converter are reporting too similar of readings


What to check
-Check for exhaust leaks at the manifold, pipes, catalytic converter.
-Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
-Inspect the downstream heated oxygen sensor (HO2), replace if necessary
-Replace the catalytic converter

Usually a P0420 will come up with after-market cat converters who do not perform up to oem standards.
 
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JEER42

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Damn it! After reading this thread now my car's cat is rattling too! What do you guys think about a test pipe to replace the bad cat?
 

lltradell

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First check the heatshield, and 02 sensor. If those are on, then your cat is bad and your gonna get a CEL of p0420 which will in turn make your car run like crap. not sure about the test pipe though. You can do the defouler/ nonfouler trick. search for it.
 
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