Thanks for the advice. I am assuming it is the exhaust. If it is the cat converter, I should have check engine light on which I don't. I'm waiting on my exhaust to come in. I'll post after I put them on. Again, thanks for all the help! =)

 

The CEL is not always the case with a pooched cat. In theory it should be on, but with me, it wasn't on. Nore was it on when i put my test pipes on. So really it's difficult to gauge the problem through that single observation.

 

Found out it wasn't my exhaust.....it was the Cat converter (sigh). I would expect the "check engine" light to come on if it was the cat but it did not. Learn something new everyday

 

Could you better explain this core rattling? Was it long after start up? I too am dealing with a very similar problem. I changed plugs and did a coil test. Same symptoms as you. Random misfire, cleares up, then persist but then stops. After slow start up.(turn key to "on" wait for pump to stop then start) it goes away. I was thinking fuel pressure. After a cold start up, first of the day she'll growl within a hundred yards of departure then not again unless it's real cold. I never have thought of exhaust b/c mine sounds REAL good. I only have 63000 on mine so a cat is not my first thought but I've been wrong before.

Any Help from anyone would be so helpful.

 

From my case, the core (honey comb shape) was moving around inside the cat converter (the rattling noise was coming from that). Once the air flow from the cat gets clogged due to core moving around. I would loose a lot of power, check engine light would come on and the whole car starts to rattle. But when the core gets in position where the air flow is good, everything comes back to normal.

When I changed my sparks and coil, I accidently mixed the wires that connects to the coil. From that, I got random misfire code and the car would rattle; also, loss of power.

If your exhaust sounds fine, then check your wires that connects to the coil. you MIGHT have crossed your wires.

Hope this helps~

 

I appreciate the response. I'll be sure to check out all the aspects and post any findings.

 

For those that are having cat problems, remember, it's an emission component is covered by the Federal emission warranty which is 8 years/80K miles. Your ECU is covered by the same warranty.

http://www.epa.gov/oms/consumer/warr95fs.txt

 

If you start getting P0300 out of the blue it should not be your coils. The odds of more than one coil going bad at the same time are astronomical. Also, if you had 2 coils go, you would get a code for each of the affected cylinders and possibly the additional P0300. I have seen P0300 happen when water gets in through the rubber grommet on the passenger side where all the wires go into the car. I had a tech put the rubber back on improperly - it looked good, but it was just sitting on top, it wasn't actually sealed. Every time it rained, I got P0300 and the car ran like crap.