I know this has been covered many times and I have done a search which gave me some ideas but just want some confirmation

For about 2 years now I have had the P0171 and P0174 codes.
I have changed all 4 O2s, Tune up, Fuel filter, PCV valve, tested vacume (no leaks).

Now I am leaning towards cleaning MAF or cleaning EGR valve.

What do you think? Am I on the right track here and which do you suggest of those 2 ideas or others?

Please help I really need to get my tag soon and I can't until I get these codes fixed.

Thanks

Stan

 

I forgot to mention this is on a 98 4.6l 4x4

If anyone has any suggestions they are welcome....really..any at all... please

Again thanks

Stan

 

did you erase the codes by disconecting your neg batt cable and turn headlights switch on to drain any extra juice after 15 minutes reconect and see what happens.

 

Stan,

A few suggestions:

1. Have you installed a FIPK or a new air filter as of late ?
The reason I ask is if you knocked one of the hoses off the intake, or the IAT snesor is not installed correctly, then you could be getting unmettered air into the system, poss causing the code.

2. You can clean the MAFS with a Q-Tip with windex sprayed on it, but be careful as not to break the wire. This is usually the fix for this code, from what members have posted back.
Side queston on this, does your truck ping under a load ? This might also be an indication of a dirty MAFS, but not the only cause.

3. When you checeked for VAC leaks, did you do this with the engine hot or cold ? The reason I ask is maybe the elbow on the back fo the T/B for the PCV has a crack that comes about with heat. If you want to try a new PCV, it has been posted that it is like 65.00 or something like that, and you get a new PCV, PCV hose, and the rubber boot for the back of the T/B.

Just a few suggestions, the loose connections if you reciently did an Air filter or FIPK, then move on to the MAFS cleaning would be the top ones.

If you did the search for P017* then it shoul dhave posted back with ~ 38 threads on this topic, and you can get the results that memebers have posted back.
Once you preform the work, remember to clear the computer before taking it out for a solid 2 drive cycle test ( 2 times over 48 mph sustained ).

Good luck and post back what happens for the next guy.

Steve

 

The PCV valve, hose and elbow will only run about $25.00 at a dealer. I paid $16.00+ wholesale for it. I would go ahead and change this out. The majority of the time, this is the culprit. The elbow usually only lasts about 60,000 miles and is hard to reach and check out. Change it, and then reset the computer and see if this takes care of your problem. Good luck.

 

the maf filament is fragile and it's best not to touch it at all. I spray it down really good with Brake Kleen or an electronic parts cleaner (if you use electronics part cleaner make sure it is the kind that leaves no residue). No need to remove the maf; just spray it well, let it air dry and you are back in business. good luck

 

Update:

Well I cleaned the MAF with throtle body cleaner. The elements were fairly dirty and cleaed up nicely.
I was going to replace the EGR vavle as well but the parts stores did not have it in stock so I cleaned it, made sure the valve would open and re-installed it.
Reset the computer and the CEL came back on at 26 miles.

The only other thing I can think of is to order the EGR vavle and replace it and something called a DPFE sensor, whatever and wherever that is.

The power does seem a little better though but I don't think it was related to the CEL anyway.

Any other ideas guys?

Also the PCV valve hose seems to be very much intact as best as I can tell.
Oddly I do not find any kind of "elbow" on it at all, the hose just circles around to the back of the intake.

Thanks
Stan

 

The elbow of topic is at the engine end of the PCV tube at the top back of the TB. I wouldn't spend the money on a new EGR just yet. If you cleaned it up and it still worked then more than likely it's fine. What you need to do is remove the TB and clean the two 5/16 EGR passageways that go into the TB. 4.6's are bad about clogging these two ports up but most of the time sets a low egr flow code. Maybe yours are not restricted enough to set a flow code but enough to cause problems. It simple and takes about 2-3 hrs to do. You might want a new TB gasket (motorcraft# f65z-9l437-a) which is less than $6. The DPFE can be checked with a digital multimeter and some specs or you can buy a new one and hope it helps.
Code 0171 and 0174 can also be set by partially clogged injectors. Let's put it this way dirt gets to injector tip and it clogs, injector is unable to spray correctly, PCM has no other way to know something is wrong other than by seeing that a cylinder on that side is burning lean.
None of these may fix your problem but it's a start and gives you some background info.

 

I had a PO171, and it was a bad MAF. Cleaning it put off the inevitable for a week or so, but the code came back and would not go away. I had a K&N fipk at the time, and for about 2 1/2 years before it went bad, so that wasn't the cause per say. If cleaning it didn't help, it very well could be a bad MAF.
Since going out of warranty, I will be taking the truck in and let them figure out what the problem is, then fixing it myself . The last straw was a cruise control servo that set me back $386, when the part was about half that and held on by two bolts, lol. My CE light is back on now, and that's exactly what I will do.,,,,,98

Mine has no elbow on the PCV valve hose either?? The hose just goes straight into the back of the TB with no other type of fitting? Maybe that was a quick dealer fix? Who knows.....

 

Thanks for all the help so far. I'm not out of the woods yet but I should know pretty soon if it is fixed.

This morning I replaced the DPFE sensor, and reset the computer again.

I have about 25 miles on it so far with 2 good highway trips down a few exits and back on the way to work.

From what I can tell the power is much better than it had been so that is looking good but I don't think the power issue I was having was related to the CEL.

I should get enough miles when I go to lunch to be confident about the fix.

I'll post when I know

Thanks again
Stan

 

I've been dealing with the same problem for 5 weeks now. All O2 Sensors have been checked and I have removed, cleaned and reinstalled my K&N FIPK kit to no avail. What is the DPFE sensor?

I received a reply by mail from the NHTSA stating that said I should inspect Air Tube and PCV for proper seating.

Ironically when I first found this problem I found my PCV to be just sitting on the hole it was supposed to be plugged into. I plugged it in and got my power back and turned the CEL off.
But 45 miles later it was back on. PCV was in fine and idle was still great.

I drove to Lake Tahoe pulling a jetski last week and did a round trip of 140 miles without the light kicking on (70 there, 70 back). But when I stopped in to Kawasaki with my Ski the light came back on - DAMN THAT LIGHT!!

 

I thought many of you may want to hear what National Highway Traffic Safety Administration (NHTSA) says about these p171 / p174 codes:

1999-2002 F-150 Lightning - 2002 F-150 SuperCrew Harley Version - DTC P0171 & P0174 - Inspect Air Tube and PCV for Proper Seating.

Some 1999-2002 F-150 Lightning and 2002 F-150 Harley Davidson Supercrews may exhibit Check Engine Light illumination with Diagnostic Trouble codes (DTC) P0171 or P0174. This may be caused by the clean air tube being over or under inserted into the air cleaner (End of clean air tube rolls up or over the positive stop tabs on the air cleaner on over insertion), resulting in unmetered air entering the throttle body. To service, first verify that the clean air tube is properly seated, also verify that the PCV valve is fully seated with the hose running under the heater hoses to prevent pull out. CLEAR DTC's & RE-TEST

 

Ok,
I went out driving at lunch and am up to 51 miles with no CEL.
It seems that I have ALL power that it used to have Woohoo!!
The CEL always came on by or about 50 miles so it is looking very good right now.

After working on this for the last month and a half here is what I have learned.

1) never trust any mechenic unless you know him well and know he will not screw you over. (spent $1000.00 for o2s which were not needed and were not even the right ones)

2) with paitence anyone can fix it themselves if they have a group like this one to get advice from.

3) Ford was stupid for putting 4 freaking O2s on these trucks to start with

4) it looks like the problem was solved in the end by either the fuel injection trreatment or more than likely the DPFE sensor which is a Differential Pressure Feedback EGR Sensor.

It took me about 10 minutes to change the DPFE out, it's right in front of the EGR valve on the 4.6L and it cost me $54.00

Hope this info helps someone else.

Stan

 

OK - I think I have read EVERY FORUM on the net to do with this problem and I have a bit of a story/ step by step for everyone.

My 2001 F-150 Supercrew had the SES/CEL come on at about 22,000 miles. This was about 5,000 miles after I installed JBA Headers, and K&N FIPK, as well as a New Mass Airflow Sensor.

5,000 miles to me is long enough to determine that the upgrades didn't directly influence the SES/CEL. Mechanics dont seem to find this error very easily as most diagnostics points to bad O2 sensors when really it just means that the O2 sensors are seeing the error - they aren't the error - they just see the error.

But mechanics default to replacement for some reason - all of them checked out fine. I was being asked to let them send it to a diagnostics location to do computer, sensor, check diagnose /$600 - I got a gut instinct to pick it up and check it first myself.

I read several sites / forums in regards to the PCV errors and trouble with the 'Elbo' from the PCV so I decided to check it out. MY PCV WAS RESTING ON TOP OF THE VALVE COVER. Plugging it back in directly smoothed the motor out and I cleared the code.

BUT - I still only went about 50 miles before the code came back!.

I then took out the Mass Airflow Sensor and blew it out with Canned air, reinstalled it and reset the code. (It was visually clean already) I drove for over 4 hours(140+miles) before the light came on again - much longer than anything else I had tried.

So I READ, & READ EVERY FORUM - THIS ONE IS VERY GOOD!

So Today I checked & reset every rubber hose I could find, listened and tested for vacuum leaks and cleaned all connections from the FIPK kit. Then I pulled out the MAS and blasted it with Carb & Choke Cleaner. I then blew it out to dry it with Canned Air again.

Oh My - I Felt an instant Boooost of Horsepower - this is the first thing I had ever done that I could notice with driving - Whoooo!

I've only done 35 miles tonight but I can tell right now that my MAS must have been dirty even that my eyes couldn't see. Maybe K&N filter oil or something. I guess over time a little horsepower lost each month made it an un-noticeable loss.

But it is Baaaack!

I think it is very obvious based on your symptons wether it is vacuum leak or a MAS problem. I had both which made it tough.

If you get these p0171 & p0174 codes and you have an uneven idle or choppy idle - then you have a vacuum leak. My idle was barely noticeable even with the PCV popped out because it was still sitting directly over the valve cover hole (Look Twice, it was visually deceiving). I didn't notice the rough idle - the mechanic did.

If you get these codes even with a smooth idle, but with some power loss and bad gas mileage - check your Mass Airflow Sensor and clean it even if it looks clean.

Pictures of my truck are here: (dont drool on your keyboard)http://www.footprintsweb.com/X_live/.../Reno_f150.htm

 

Well crap!!

On my way home after work today the CEL came on again

The up side is that I have already passed emmisions and have my tag so time is not a critical as before but this is really ticking me off!

Last week the CEL would come on before I made it 30 miles.
After the DPFE sensor and half of the second tank of fuel injector cleaner it stayed off for over 140 miles.

I plan to take it to have the codes pulled again just to confirm it is the P0171 and P0174 codes again and not something new. but what do you guys think? Maybe another tank of fuel injecter cleaner? any other ideas?

TIA
Stan