i have a 1997 xj 4.0 tring to get smoged its been tripping two codes 300 and 301. to start with i just changed the cat and muffler both o2 sensores but this problem exsisted before that ive also changed the plugs wires cap and rotor just dont know where to look now help please

 

I assume you mean P0300 and P0301? Those are multi-cylinder and cylinder #1 misfire codes. How does it run? Do you notice a misfire?

 

Anytimes I see the P0300 (random misfire), I start by verifying fuel pressure.

Must be done with a gauge; no shortcuts. Many parts stores will rent you a gauge inexpensively.

For a 97, you should have 49 psi, plus or minus 5 psi. Start there; fuel pressure is one of the first thing any technician would verify if you were to bring this into a shop.

 

yes i am refering to po300 i have a presure test just have to find it thanks to you both