I know this has been talked about in other posts, but I don't have the time or am willing to do a complete search. I'm getting a very random P0304 error code on my 2007 Ranger with the 3.0 engine. I can drive it for several thousand miles at highway speed and never get the code. The Check Engine Light will only come on in a prolonged idle situation. After a few miles, it will turn off automatically. I replaced the Spark Plugs, and all the plug wires a month ago. I put the truck in the Ford dealership to have them diagnose it. After they had it for two days I was informed that they were doing out of business at the end of Fedbruary (2019) and that they could not work on or properly diagnose the code. However, the Service Manager said that it could be the Head problem involving valve seats. But he wasn't sure! It seems that their only technician who could work on it left the week before and he took all the diagnostic tools with him.

So I took the truck to a local non-dealer garage to have them check it out. He also said that it could be the head problem or maybe something else. He did a compression test of cyl 4 and 5. He said that it didn't look bad but was suspicious. He didn't want to do a valve job on the truck unless it was sure. He said the compression test was inconclusive! I don't notice any driveability problems, just that annoying light comes on every now and then.

So here is my question. Is there anything else that I could look at or replace that might cause this problem. I would gladly put it in the Ford garage to have them diagnose it, but the closest dealership to me is over 50 miles now. If I need a valve job I will have it done. I just want to be sure first. Any suggestions?

Well first of all of course a compression test will be inconclusive if he only tested 2 cylinders. You need to test all 6 cylinders. First dry for a baseline and then followed by a wet compression test in order to diagnose a valve issue. Find a new mechanic, or do a proper compression test yourself. Compression testers aren't that expensive and the test is easy.

since the misfire is isolated to cylinder four, and not consistent I would check the #4 injector and harness, check for any leaks (oil, coolant, whatever) on the #4 plug, and swap the coil packs around to see if the misfire moves to a different cylinder. (Highly unlikely its a coil pack issue but its simple to rule it out.) Also check the condition of the #4 plug. Was it cleaner or oilier than the others when you replaced it?

Well, I'm pretty convinced that the problem is the valve seat. There are no other shops I can take it to. The Ford garage is closing up shop in Mojave near where I live. There is only one Auto Repair Shop in my town. The mechanic there says he is 80% sure it needs a valve job but doesn't want to do it until he is sure. He said he would feel terrible if he did the valves and the problem came back. There was a time when I could do the job myself but I'm too old for that now. I'd rather pay someone to do it. I was just hoping that someone else had this problem and found a different cause.

Has anyone on this forum had to do a valve job on a Ranger with the 3.0 to correct the P0304 problem?

Well, it is official. I'm tired of looking at the Check-Engine light for the P0304 and P0306 code. I put the Ranger in the Ford Dealership to have them install a Limited-Slip differential in it, and also asked them to verify the reason for the Light. They said there was a 20% compression loss on cylinders 4 and 6. Not a big surprise there. If it weren't for the strict California Smog laws I wouldn't have to bother with it. The light does come and go. The truck would not pass smog for any kind of CE light on.

So, on February 14, 2020 it is going back in the shop so they can fix it once and for all. They are going to do both heads at the same time, so I won't ever have to deal with this again.

I did find out that there was an emission warranty back in the day. However, my truck is a 2007 with 161,000 miles on it and is now far out of warranty. Too bad. But this is the first time that I have ever had this truck in the shop for a serious repair. So I guess I'm due. Too bad they have to take the heads off to fix it though. The cost will be $2,000.00

I could have pulled the heads myself, but I'm just too old now to be doing that kind of work. I just want it done with, and done correctly!

Well, I guess I'm going to save some money on the Ranger repair job. The Ranger was stolen out of my driveway two days ago and tried to outrun a police car. It didn't end well for the 16 year-old non-licensed driver or my truck. It hit a telephone pole and is totaled. Can you believe it?

Ugh!!! Man, so sorry to hear. I hope that you're able to find a replacement vehicle as quickly and painlessly as possible.

I do have insurance, but Lord only knows what they will give me for a 2007 Ranger with 160,000 miles on it. I'm semi-retired and really can't afford to lay out another $25,000.00 or so for another truck. I'm just going to have to wait and see what they give me for it, and then see what I can come up with. It would seem to me that the parents of the three juveniles who took it owe me a new truck. Just sayin!

I so agree! Unfortunately, the days of responsibility seem to have disappeared. If I had stolen someone else's truck and tried to outrun a police car with it, my dad would have a) let me rot in jail, b) addressed the issue with the parents involved, and c) worked me like a rented mule to get his money back the moment I was released.