P0304 misfire troubles.

[1986b2000]

The car has been throwing this code since I got it in June. I've only really been driving it for 2 months and this crappy 10-13(90% highway) mpg is killing me. The engine shakes noticeably. The coil is orange and the wires are blue and look like they were replaced be previous owner. Thr plugs look goodreplaced too. The #4 plug was black so i swapped it with #1 and the miss stayed on #4. Swapped the #4 wire with #1 wire and the miss stayed on #4. Swapped out the #4 injector and it still misses. Today i pulled the wire off the plug and its not getting spark. It isn't getting spark off the coil or end of wire. I know it will throw two cylinders at once so i checked 1 and 2 and they both have spark. What would cause no spark at the coil on only #4?

[ptcruisersteve]

I would suggest checking the coil wire for cylinder #4. Sometimes they have bad connections.

I would suggest making sure cylinder #4 has compression. You might have bad valves. Has it been gradually getting worse?

Check your PCV hose coming from the engine to the manifold. The hose might be bad going underneath the manifold.

How are you testing for spark?

[Probedude]

Originally Posted by 1986b2000

Today i pulled the wire off the plug and its not getting spark. It isn't getting spark off the coil or end of wire. I know it will throw two cylinders at once so i checked 1 and 2 and they both have spark. What would cause no spark at the coil on only #4?

Like PT Cruiser Steve wrote, how do you know you're not getting spark to the end of the wire for #4?

You are correct that 2 cylinders are fired at once - the secondary of the coil, one end goes to one plug, the other end to the other. The fact cylinder 1 fires means the other end of the secondary is finding a path. Since you swapped wires and it's following "plug #4" (or really the output of the coil to plug #4), your coil is the likely suspect.