Did you put a new coil pack on cyl4? They have a habit of being ****

 

I swapped the coils on Cyl 3 and 4, the code did not follow, so the coil should be fine.

 

maybe it works.. intermittently

 

But I've switched them, and left them switched. Same problem, same cylinder. If the problem presented itself AFTER I've switched them, wouldn't it be on Cyl 3 instead of 4 (which I switched with)?

 

Should have my compression test kit tonight. I'll run the numbers this evening.

IIRC, the compression should sit somewhere between 120-140psi, correct?

Also, IF my compression is good across the board, what else could cause my symptoms?

 

Ok, compression tests results are in.

I did two passes on each cylinder. I tested each cylinder one at a time, then started over for a second pass. The cylinders were tested front to back. I did the test at operating temp.

Cyl. 1. 143, 145
Cyl. 2. 145, 150
Cyl. 3. 135, 139
Cyl. 4. 155, 159 (This is the trouble cylinder throwing code P0304)

From what I understand minimum PSI on a cylinder is at 101 psi, so I guess I'm within the optimum range. I have a 12 percent difference between the lowest PSI (3) and the highest (4). My guess is that it is not a piston ring/cylinder problem.

Thoughts?

 

Yea those are good numbers, all in range at any rate. I'm not sure where to go now. You've swapped injectors and coil packs, I wonder if the wiring to those is good if you've got some something intermittent there.