I just joined and this is my first post. I have a 1999 SC1. The car began to run very sluggish and the cat would run hot if drove at normal speed. I took it to a muffler shop thinking it was a cat. conv. problem. They did a code check and they got p0300 and p0340. They said a misfire will cause the computer to "dump" fuel into the cat which will ignite and heat up and it was an engine problem. They said that the exhaust was fine (at the time). It did run okay until I arrived at the muffler shop, But after they let it run idle for a little while it began to bog down again. It would run okay if I let it sit without starting it. To make a long story short, I have a SES light flashing. I changed the plugs, wires, ECTS, TPS, Thermostat, the ICM is less than a year old, and I checked resistance on both coils. Now it has no power as soon as I start it. Is there anything that I might have missed or is it possible that the cat is ruined due to driving it between now and when I took it to the muffler shop?

 

The VERY FIRST thing get the codes read and then come back with those CODES and ask questions. ECTS did it come from the dealer, and did you splice in a new connector that was bought from the dealership?

 

The codes P0300 and P0304 by themselves are not very informative.
What is happening is the computer uses the crankshaft position sensor and can monitor the speed as it passes by. It has a time window to compare to and if it does not pass by at the prescribed time interval it assumes a missfire. As it knows when each cylinder fires it can tell you which one did not fire to give the wrong reading. It does not tell why it missfires just that it did not fire, so further information is needed.
So, if there is something going on bad enough to cause a missfire than there also should be additional error codes which would help point at what ever is going on.

 

The codes were p0300 and p0340