Hey all- so I had a misfire code a few weeks ago, and found out it was an ignition coil that had to be replaced. I replaced that, all the spark plugs and wires...but am still having a pretty nasty misfire. When I started up my car (for the first time in about 2 weeks) a bunch of white smoke came out the back tailpipe for a minute or so, and it reeked of rotten eggs. The code i was getting on my OBDII reader was a P0300 multiple misfire.

I did a bit of research and found out that there's a very good chance it could be a bad catalytic converter. Thoughts? Thanks much

 

Bump* Any help much appreciated

 

rotten egg smell generally points to a bad cat, you can start there and see where it gets you

 

Rotten egg smell is from the cat doing its job on a rich running engine, which is what you'd be getting from a misfire. Diagnosing the random cause though is hard to do online, as it could be from a number of different things.

 

Cat check is pretty simple, You just check for back pressure in the exhaust. I am not use to a bad Cat causing random misfire. Since the bad Cat effects all cylinder equally the computer normally has a tuff time seeing anything wrong. I have seen many cars with Cats so bad they would no longer start and still not have any stored codes.

White smoke would indicate lean. Fuel pressure?

 

A quick search on the internet shows what the code means.

OBD-II Trouble Code: P0300 Random/Multiple Cylinder Misfire Detected

Some believe that it's a code that relates to after market parts. Before you replace your CAT I would do a simple spark test on each cylinder to see if there is a problem before or after the spark. Spark testers are cheap and the can point you in the right direction. Since you replaced your plugs, etc. you could be looking at an exhaust issue.

 

All- thanks a ton for the feedback.

Does anyone happen to know the size of the exhaust pipe that goes into/out of the cat? I have all stock piping until the muffler. Is it 2.5-3in?

Thanks much,

Robby