First I have to admit that in all these year I have never personally checked my PCV valve. The truck has been serviced a few times by the dealer... a few times by the local mechanic, but I don't ever recall anything being done with the PCV valve. At any rate... it's a 2002 4.2L V6, and while looking over some of the electrical tests that I could perform on some of the emissions, I came to the PCV valve, not realizing that it was on the passenger side in back... I had always thought it was next to the dipstick on the driver's side.

Now to the question: The driver's side is just a PCV sized plastic elbow in the grommet and a plastic tube that goes into the air cleaner manifold. On the opposite side I expected to see the actual PCV valve. To my surprise, there is another PCV sized plastic elbow in the grommet, with an attached air hose that looks worse for wear.

so... what gives with that??? I mean, number one, why would someone... and secondly, I assume I should actually put a PCV valve into the valve cover, right? And probably get a new hose for it? I am getting 2 codes, P0171 and P0174, and probably have been for a Loooooooong time.

Thanks in advance for the comments!

 

those are lean codes. If anything you need to replace the elbow on the PCV. Your losing vacuum somewhere. prolly in that hose you talk about. PCV is only on one side.

 

The PCV is either located in the passenger side valve cover or on the side of the throttle body. If that hose is rotten , it most likely is the cause of your lean codes like KR newbie said. It may have 2 small water hoses attached to it also, if it is the heated type. Don't remove the water hoses if there is pressure in the cooling system.

Which intake plenum do you have, plastic or aluminum?

 

The elbows on both valve covers are identical. I expected to find the PCV on the passenger side with the coolant hoses you mentioned wrapped around them...but now that you say it's on the throttle body, that makes sense. That's what the passenger side valve cover hose leads to, and it has 2 Robertson screws (square drive). I'll have to check that out.

The plenum is black plastic. Why do you ask? (loaded question)

 

I asked about the plenum because I think when they changed from aluminum to the composite one is the same time the PCV moved from the rocker cover to the throttle body.

 

If you have the plastic intake, lean codes are frequently caused by bad plenum gaskets and isolator bolts.

 

yeah, last night I found a website that has great illustrations of the repair process to replace the isolator bolts, so you might be right about that glc. The valve cover on the passenger side is pretty oily but I wondered if maybe that was from leakage around the PCV hose grommet/elbow. Would any oil come from a cracked intake?

Generally the engine has good vacuum, around 20 in-Hg. Once it did idle rough and dropped to 15 in-Hg but I assumed that maybe the computer mistakenly signaled the EGR to open, because it sounded similar to what you would expect if you hand vac'd the EGR during idle. Shut off the engine and restarted it and it was idling normally again, albeit too fast. (classic vacuum leak)

I'm running out of places to look for vacuum leaks. Replaced the PCV hoses this evening (the old ones were rotton like you said jgger, kind of loose fitting from getting soft and stretched out). Doubt it will make the difference, but we'll see. They fit 100% better than before! The PCV valve is crazy expensive... $35! So I cleaned and blew out the old one, it seemed fine. I assume it is like a small thermostat and it's supposed to be closed at cold temps until the coolant lines heat it up? If so I better check it cold and will replace it if need be.

 

After I chased everything down on mine it ended up being the isolator bolts. Get the ones from Ford, they're crazy expensive too, but they are the best.

On the PCV the heated system is to keep it from freezing up in cold climates from condensation in the system. There is an o-ring on the PCV that can get hard and cause a leak also. I just bit the bullet and replaced mine because I couldn't find a replacement o-ring.

Also on mine I just did the isolator bolts and upper gaskets and that has been about 100 to 120k miles ago and no issues at all.

Put isolator bolts in the search box and you can pull up quite a few threads on them. Plus I think there is a step by step DIY in the how to section.

I would clear any codes and drive it with the new vac and PCV hoses and see if that cured your problem. If it didn't then you are more than likely needing the isolator bolts.

Good luck and post up the results.

 

The o-ring that gets hard... is it the one that seals the PCV valve into the throttle body? Because I was thinking it looked kind of hard too. I put some axle grease on it before I stuck it back in, in case it might help it seal. Figured it couldn't hurt.

I've come to the same conclusion... if after I have checked all vacuum hoses... pressure tested the EGR... and replaced the fuel filter, if I'm still having lean issues then it probably is the isolator bolts on the plenum letting a bit of air in- post MAF. I'll probably need a 3 day weekend to do that one. But I'll definitely come back and post what I find.

 

Yes that is the 0ring I was talking about. I actually did the grease thing too.........it didn't work for me. Ford does not sell just the oring either. If you could find a fuel resistant one you could replace it, I couldn't find one myself.

Good luck, I hope what you have done so far fixes it for you. BTW I work slow and am **** when I work on my motor and the job shouldn't require a 3 day weekend.

 

The P0171 and P0174 codes are no longer reoccurring since I changed the O2B1S1 and the O2B2S1 heated oxygen sensors.

However, after clearing codes and driving about 200 miles, I am now getting P1131 and P1151 codes. The freeze frame seems to show that this error code is continually popping up at low RPMs- perhaps when I let the clutch out such as when taking off from a stop or at idle, on CL (closed loop) when the SHRTFT1/2 is at 32.2%. (at idle)

SHRTFT1/2 seem to run closer to 0% at idle when it is on OL and CL-Fault. I'm wondering if that means anything. Idle is generally high (around 1100 rpms) but occasionally something will "click" and it will idle down to around 850 rpm, which seems more normal.

Any ideas?

I took the PCV hose off the PCV/throttle body at idle, and it was sucking pretty hard. When I let it go you could hear it click closed... and when I let off you could hear it click open. I think it's operating normally. I might still replace it due to that O-ring, but it doesn't seem to be leaky.

I need to do some more checking into the EVAP vacuum lines. They are a little more difficult to trace. Should those lines hold pressure if I plug one and pressurize the other?

 

The 1131 and 1151 codes indicate slow switching, I believe for the rear O2 sensors. Given your high idle you are probably still having the vac leak. You could try changing the sensors but that will cost you. Since you are planning to do the plenum gaskets and isolator bolts, that's what I would do first and see if that does it.

The old sensors may not be able to keep up with the new front ones that are trying to keep up with the vac leak.

 

Nope, those codes are for both front sensors.

 

And the rear O2 sensor's don't tell the computer to make any sort of adjustment, right? I've heard it's a waste of time to replace them, unless you're in California and have to pass smog.

 

All the rear O2's do is report on cat efficiency.