PO300, PO301, PO303

Question

I have a Kia Spectra with codes PO300, PO301, PO303. I have ohm tested coil packs, injectors, checked and changed plugs, noid light tested injector wires, switched injectors 1&3 with 2&4, found the cats were bad and changed them out and still got the same code. Compression is 205 straight across. It has a 1.8 liter engine.

Answer 1

P0300 Random misfire

P0301 Misfire number 1 cylinder

P0303 Misfire number 3 cylinder

Cylinder 1 and 3 are companion cylinder if this has a coil pack then problem would be with the coil pack when number 1 cylinder fire number 3 also fire on the exhaust stroke. Faulty coil packs can do this, What also cause a misfire like this would be a timing belt. timing belt marks should be checked

 These are coil packs if number 1 cylinder misifires and number 3 misifre then the problem is with the coil pack.

 If you have individual ignition coil do a running compression test. With the compression at 205 straight across you should have more that 65 psi.  It would also be a good idea to check the timing belt marks,