I have an '02 F-150, 4.6ltr, 87K miles. Runs great but today I noticed the engine begin to run a little rough when I come to a stop; the tach bounces between 1K and 1.2k. The CEL came on shortly after teh engine began running rough, My generic code reader reported error codes 171/174

Any suggests what the problem might be?

Thinking it might be the O2 sensors, I found the "How-To" - O2 Sensor Install by JMG-in-Alaska (which was well done) but was hoping there might be a more likely problem.

Thanks for any advice provided. - rc

 

I would check for vacuum leaks first off.

 

If you look in the "search" section of this site above, and click it open, type in PO171 or PO174 Code in the "search forums section. You will find everyhting you need to know about these 2 pain in the butt codes. There can be alot of things to check for concerning these codes. I ran into this problem a year ago and the other members on this site walked me through the things to check and or repair. Mine came down to cleaning my MAF Sensor and replacing my PCV assemply. The rubber elbow on the end of the PCV Assembly that connects to the throttle body DRY-ROTTED and had a hole in it. I cleared one code by cleaning the MAF and the other by replacing the PCV Assembly that included the rubber elbow. ($28.00 from Ford)
I'm not saying this is your fix but it is a couple of things to check for.
If you use the search section, you will probably find the thread topic I started and it will walk you through all the advice that was offered to me and the checks and repairs I made.
The O2's can cause the eratic running, (seen that happen on a few vehicles) but make sure you do all the obvious checks before you start throwing expensive parts into it.

Good luck & keep us posted on what you have done, checked for, repaired, etc. We can help you as long as you keep posting and give us accurate info.

TJKinCNY

 

Those codes mean both banks lean. Your O2's are fine, they are doing their job. Most likely a vacuum leak, and the PCV elbow is the most likely place to find it.

 

I purchased a new PCV and elbow (motorcraft) but cannot find the actual location to install it. I looked on the valve cover (both sides, driver and passenger) and cannot find it. There are hoses connecting to the top of the valve covers that look like where I have found PCVs on previous cars/trucks but these hoses only connect to a plastic hollow fitting that plugs into the valve cover. I went to a Ford dealership and asked the parts dept desk where to install it and they showed me a mechanical drwawing that indicates it should be installed where the plastic hollow fitting currently is (??). I'm curious if anyone is aware of any 4.6ltr engine design changes that change the usual location of the PCV. I appreciate the advice I have already received. I think I am overlooking something simple. Thanks for any advice

 

 

Guys, I do appreciate all the help and advice. However, I am still trying to change the PVC. The photo (in this thread) identifying where the PCV valve is at on an '02 4.6 is pretty close. It is located on the rear of the throttle body/intake manifold (the PCV is tucked way back against/below the firewall). The hose from the valve cover runs to the PCV valve (the hose also runs directly under the heater core hoses which makes removal a little more challenging).
The PCV valve itself also has 2 smaller hoses connected to it as well (??). I am trying to determine if the PCV valve is thread as it does not seem to just push in.
The VIN number on this truck also indicates the engine is a 4.6ltr (Windsor) however, everytime I go to the Ford dealership to buy parts, they give me the wrong one. (??)
Anyway, has anyone seen a 4.6 Ltr V8 with the PCV plugged into the back of the intake (with 2 smaller hoses connected to it)? If so, how is it the PCV connected (threaded in or pushed in). I really do appreciate the help I have received and any additional assistance is greatly appreciated.
BTW, I have had it looked at by a professional mechanic and he did confirm the problem is a split in the PVC hose. They were just unable to get the replacement hose for 3 days.

 

The valve itself is probably fine. It's the elbow that he has circled that rots and cracks.

 

I agree. The hose (elbow) has a hole in it. The location of the hose (elbow) is almost impossible to to get to with hands, a screwdriver, knife etc. When I am close to it, I risk banging against the upper/lower heater hoses. I really need to remove the PCV assembly to adequately remove the hose/elbow (or what remains of it). I don't know if the assembly unscrews or pops out. I can use force but if I'm doing it wrong, I could possibly break the assembly. The design/location is bad...

 

You could always remove the throttle body to make it easy. The throttle body needs to be cleaned as a maintenance item anyway so you should do that while your at it.

 

Just want to say thanks to everyone for the info I've come across so far. I have been searching through the forums and have come across a similiar issue as rta.
My 98 4.6 doesn't have any elbows on the pcv hose. It is an insulated "hard" hose with soft hose ends that are straight. I found that the valve end soft hose had been worn through right were the insulation ends. I was able to get a short scrap piece of hose to replace it, and had my codes cleared at the Advance Auto down the street. Only issue now is that the truck is running rough (almost stalling while in park or at a light) w/o a CEL. I intend on getting the spray and cleaning the MAF when payday comes; hopefully that'll fix my issues. I'll try to get a pic of the hose that I have.
Sorry if I may have ranted. I have a tendency to sometimes over-explain thing to folks.