2002 Ford Taurus codes P0316, P0304, P0305, and P0306
 

I have a 02 Taurus and I get code P0316, P0305, P0306, and P0304. I have already change the plugs, coil, EGR Sensor (it was bad), and plug wires but obtain the same results from diagnostic reader. The issue I'm having is my engine runs really rough at idol but seems to run fine at higher speeds. I put a stethoscope to my injectors and it seems my two front ones, I think injectors four and five seem not to have much sound. It seems like I might just be hearing injector 6 from 4 and 5. I saw on a YouTube video that a mechanic had the same code P0316 and P0304 and had replaced everything I did but found out it was a bad injector.

Should I try and replace the injector next?

Have you checked the PCV hose and PCV valve ? Start with the simple things first. Codes seem to be indicating one side of the engine being affected.

I've Changed the PCV Valve about 3 - 5 months ago but I have recently taken if off and checked that as well and it is in working condition.

As with many here I have seen this same issue many times, and just about every one of them had a differing cause. May I ask which motor you have, (Duratec vin: S, Vulcan vin: 2 or U)?

Have you checked for lose, dirty or broken grounds, mainly around the left (forward) head.

Rule out a leaking gasket by spraying starter fluid around the matting surface of the intake (upper and lower), as well as the IAC and throttle body with engine running, any change in idle?

You changed the DPFE (EGR sensor) was there a 1400 code? Can you test the EGR itself? With engine running remove the vacuum hose and, using a vacuum pump, apply vacuum to the EGR, does it stall or remain the same.
Check for lose fitting, cracked or leaking vacuum hoses.

Repeating hankys suggestion (who has likely forgotten more than I will ever know) did you replace the PCV valve or shake it. I hear many say if it rattles when you shake it it is good, wrong answer. The spring inside has a set tension, impossible to test and very cheap to replace. The PCV hose on these motors are infamous for cracking also.

I could go on but this should give you some typing to do LOL. Warning: I tend to get long winded and overly explanatory…

Sorry in advance.
Good Luck

Thanks ModestRick,

I have the Vulcan engine type.

I've changed all my upper gaskets in the past month so those are fine. I do have very minor oil leakage around the oil pan and I believe near my heads which leaks on my CAT and causes smoke every once and a while.

When I changed the EGR valve there was no code. I had noticed a broken hose before changing all the upper gaskets. I can attempt an EGR test and let you know the findings.

As far as the PCV valve goes, I do recall shaking it recently and hearing it rattle but from your saying it sounds like it's not suppose to? How sensitive is that retention spring suppose to be because I remember getting it when it was new and it rattling. When you buy the PCV from Ford, it comes with the valve and hose so both are replaced.

I went ahead and removed the injectors that I think are bad and I'm going to replace those.

I'll let everyone know the final result.

yes it should rattle, look forward to your next post.

FAILED! I replaced the injectors and the engine is still running the same. (At least I know those are good)

When I replaced all the upper gaskets and the EGR the engine ran like brand new but then slowley began to run rough again so I would like to say it has to do with something in this upper region but it's only a hunch.

As I am fiddling with the PCV valve I am noticing that it's really spongy around the washer as if it's not getting a tight fit so there could be some air leakage in this reagion. I'm going to try and tighten that up (seal it up) some how to see if this makes a difference.

Is the pCV supposed to come out really easy or should it have a snug tight fit in the rocker arm cover?

The PCV should fit snuggly into place and a PVC grommet is rather inexpensive at any auto parts.

You replaced the EGR, not the EGR sensor (DPFE)? Question: did you remove and flush the EGR tube and check the vacuum lines? You said there is no 14 code present so it would be an extreme reach to think the EGR could have picked up carbon from the tube causing it to stick open.

You checked the grounds?
You are getting the same codes? Only affecting the left head, not random?
Did you torque the manifold gaskets as per manufacturer suggestions? Checked them as described above?
(I had a Buick come to me not long ago with a similar problem. The owner replaced an alternator and over-torqued a bracket thereby cracking the corner of the upper intake. Without the starter fluid check I would have never found it.)

Sorry, without being there it is a little time consuming to help, but happy to if you are willing to accept.

Have you performed a leak down test, or checked compression?