P0316 and P0304 codes
 

I have a 2003 V6 4.0 with about 146000 miles and it is throwing the codes P0316 and P0304. The truck is idling poorly and seems to shudder whenever accelerating. The 316 code is a generic code for a problem within the first 1000 rpms and the 304 is a misfire on cylinder 4. It seems there is a lot of posts about this happening with the 3.0 but not very common for the 4.0. Ford dealer said the upstream O2 sensor had no reading so I replaced it myself and still have the same problem. I replaced the plugs and wires and still nothing. I cleaned the MAF. I put injector cleaner in thinking maybe one of them was stuck and it might break free. I checked the ohms on the injector for cylinder 4 and it came back as 15 something which seems normal. I also did a compression test on the cylinder and it came back as 140 which also seems normal. Nothing has worked and I don't know what to do at this point. I'm thinking maybe just replacing the injector on that cylinder and see if that's it? I know there are a few other possibilities but I wanted to hear from you guys. Thanks

Re: P0316 and P0304 codes
 

Compression seems reasonable, the fuel pressure is good enough to work the other cylinders, and plugs/wires shouldnt be an issue. At 146k miles you have to consider fuel pump (test by checking fuel pressure) and the coil pack. Beyond that, there isnt much else besides deep engine crap that can cause a misfire- and deep engine caused misfires are going to show up as low compression.

If it were me, Id check the coil pack for cylinder 4 operation. I would prolly get an old spark plug, hook the spark plug wire from cylinder 4 to the old plug, ground it, and see if it sparks (check for spark while a buddy cranks or while its running- be careful not to shock yourself). Be sure to do this where nothing flammable is around. If it doesnt spark, you can ohm out the coil to verify its bad. Has the coil ever been changed? Id lay 95% odds its a bad coil...

No the coil has not been changed yet. I will run that test for the spark plug in a few minutes.

Just ran that test. Plenty of spark

Re: P0316 and P0304 codes
 

Well, a cylinder needs air, fuel, compression and spark at the right time to fire. Youre getting air and compression is ok. Youre getting spark, though we dont know if its at the right time (though seriously I cant think of how it wouldnt be). That leaves fuel. I know you ohmed the injector out, but that doesnt mean it isnt plugged or isnt getting current. Can you swap injectors between say 3 and 4 and see if the misfire codes move to cylinder 3?

I would still say its possible the coil is bad IF it werent for the fact one of the codes indicates it happens right from the start. Usually a coil when it starts to fail will fail under certain circumstances but work during others. I still wont rule it out completely, but try swapping injectors and see if you can move the problem.

Im surprised someone with more experience hasnt commented- im not too familiar with the 4.0s and so im kind of shooting from the hip...

I have a friend I'm going to take it to tomorrow to run some diagnostics on it. If we don't figure anything out I'll swap the injector with one from another cylinder

Re: P0316 and P0304 codes
 

This is an interesting issue. If you get the chance and have the inclination, let us know what the solution was so we can save someone else the frustration. Good luck...

Turned out to be a bad injector. I swapped the injector with another cylinder and the misfire moved with it. New set of injectors on the way. Not sure how the injector ohmed out and was still bad. Maybe it was stuck open or closed? Not really sure. Anyways new injectors all around should put her back in tip top shape

Re: P0316 and P0304 codes
 

Ill be damned :hmmmm: Well, stranger things have happened. At least it didnt turn into a total nightmare to find (misfires can be that way).

Still, injectors arent a common failure point on any Ranger engine/model.

Yeah glad to finally get it solved. Ordered from auto zone and did ship to home and got a coupon code to save 20% so I'm a happy man. Thanks for the help!

Re: P0316 and P0304 codes
 

Wished I'd have gotten to you sooner, I'd have suggested going in there with a longggg screwdriver or piece of metal and, with the engine running, put one end against the suspect injector, the other against your ear, and listen for the chatter. No chatter means bad injector. A much quicker initial test than the swap injector method.

Re: P0316 and P0304 codes
 

I should have thought to have him do this. I do it all the time as a regular maintenance thing (listening to valves/bearings/pumps/pulleys), but didnt think of it here :mad:

By mentioning it, he nor I will ever forget to do it in the case of potential injector issues.