Im new to the site and I have some questions.

Im getting codes P0420- catalyst system efficiency below threshold bank 1 and
code P0301- cylinder 1 misfire detected.

The cat is bad and has been going bad for a couple of months. 2 days ago i noticed this loud sound louder than a tick but not nessicarly a knock. I checked the codes and go those 2. I checked the coils and no residue or oil build up on them. I switched coils 1 and 3 seeing if it was the coil pack, no change. I then replaced the spark plug in cylinder 1 with a ngk plug and no change still makes noise and cylinder 1 is misfiring.


No overheating, theres a little liquid coming out of the exhaust but its just like specs of a drop. I dont notice a sweet smell. I was thinking the head gasket.
Also before the sound if i turned my A/C on my car would idle rough and it would sputter coming out of first. The rpm would not move though. Theres no visible leaking on or around the valve cover. The sound is most definatly coming from cylinder 1 area near altenator.

My questions are, Has this happend to anyone and what should I check?

The car has 168k on the motor and its the stock D17 vtec motor.

Thanks

 

Change the second o2 sensor, it fixed my P0420

 

p0420... you know the answer there.

misfire:
Have you checked valve adjustment?

Compresssion test?

How does it run?

 

The car will start up no problem and run. Just kinda hesitates a lil when im in first but after that its fine. Its not running hot. Not leaking anything. Oil level is good it needs a change though.

It just started making the noise the other day. The A/C promblem has been 3 weeks. The car will run with it on but it bogs it down some. It has not been stalling. I dont red line it, I shift at 4-5 k rpm everytime. I only drive it a max of 10 miles a day through the week.

Im taking it to a mechanic tomorrow to get a compression test done and to see if its a quick fix that im overlooking. I know that the cat needs to be taken off or replaced or it will happen again after its fixed.

Also my gas mileage has not been effected that much im still getting around 30-32 mpg which was about normal from before.

Thanks guys

 

don't mean to revive an old thread, but what exactly did you do to solve this problem?


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It was the altenator the whole time. The belt was too tight and stripped the bearings making it really loud and unpleasnt.