Cool I can try replacing the coil packs then, just thought if they tested good, they were good.
Got the p0421 the first time I got the p0300 light, after the converter was replaced... So what's that mean?
Please read my last post:
http://www.mazdas247.com/forum/show...random-misfire-symptoms&p=5607479#post5607479
Now we have the P0421 code also. It is a pending code that only occasionally lights the CEL. P0300 will be followed by P0421. The fact is that extended occurrence of misfire ruins the upstream cat. The FIRST time your car stumbled or threw on the CEL, you SHOULD HAVE stopped driving the damn thing. These cars are so crappy that they can't handle a minor malfunction, it's like a chain reaction. 1 thing leads to another.
Please read what I wrote about coil packs. I have a set of defective coil packs in my garage. They WILL test fine. The test does not cover heat absorbed dielectric strentgh. The test only checks coil resistance. Who gives a crap about coil resistance? What kills these coils is heat. When they get hot, the high voltage spark finds other paths to ground, causing random misfire. If you take the car to a shop, their multimeter won't test the resistance to high voltage. They just check static coil resistance. Only a dead open coil or shorted coil would fail a resistance check.
These cars are garbage as far as a Japanese branded car goes. Must be Ford's influence, as my co-workers Lincoln LS has the same problems.
And if you are still getting P0421, did you clear the previous code?
Is the new cat of decent quality?
Did a P0300 occur anytime after the cat was replaced? If it did, your cat is likely damaged again. If you search P0300 and P0421 codes, you'll find some people have replaced their cats several times without ever replacing their coils. A cat costs at least $270, so that's expensive multiple times! Remember, bad coils will allow raw fuel into the cat. The fuel will burn inside the cat which damages it. Bad MAF? nope, won't destroy the cat. Neither will a bad EGR. If you've had a P0300 recently, change the coils. Both of them. Then go get your cat replaced under warranty and don't tell them what happened otherwise it will be a recurring bill for you.
Yes these cars suck. Wait until you find rust in the doors and wheel wells. Icing on the cake..........