Ok guys, Here we go. I have had the infamous P0171 and 174 codes off and on for about 10 months now. I have taken the truck in twice to a mechanic who I know and trust and have had diagnostics run 3 times. This is what has been done up to this point. The truck was checked head-to-toe for vaccum leaks and none where found. The MAF, IAC and butterfly on the intake where all inspected and cleaned. Two days ago the truck started acting a little different than all the times before with the same codes. Upon sart up, the truck would idle ok and then after about 5 min. it would really start struggling to stay running. Surging and bogging really bad. I noticed that when put into Drive or Reverse with my foot on the brake it would get worse and almost die until I gased it to get going. At stop lights it was doing the same thing. (Surging, ideling high then low). After being on the highway for about 30 min to an hour and starting my work day, the truck would run fine other than the occasional knocking and pinging and sometimes a little flutter in the idle at a stop light. Anywho, I had the codes read again that day and there were two new ones to add to the mess. P2195 and P2197. (Stuck Lean Both Banks). I took it back to my guy and had him keep it over the weekend where he proceeded the process of elimination again. After scanning and having another ASE Mechanic buddy of his look over my truck he siad that the o2 Sensors were working (Going rich-lean-rich-lean for a while and then would stick lean for a second or two). The sesors were taken out and cleaned and showed to be working properly. To make a long story short, I picked up the truck last night and was talking to him about what he had found this time. This is what he told me: The intake cover (Black plastic thing on top of the motor) has a vaccum leak and the HOS(Heat Oxygen Sensor)is having an electrical issue by not heating up when the key is turned on initally and only after the truck is good and hot does it act right. My question you ask???? Has anyone ever heard of this and would it be something I could do myself? With the arm's length list of possibilites for these codes, I've tackled just about every one of them except for this. I trust this guy and he is very honest about what he does. The challenge is leaving the truck with him for long periods of time. I work out of my truck as a Contractor and I don't make money when it's in the shop. He know's this but can't do his job either. He's only charged me $125.00 total for the 3 times he's kept it to run diagnostics and look for the problem. A heck of a price compared to what the "stealership" would have raped me with. Thanks guys for listening and I appreciate any feedback.

2004 F-150 Heritage STX
4.2L V6
52,000K
Flowmaster Exhaust

 

Coordinate it with him to leave it with him for a minimal period of time, and rent a truck.

 

I will have to say first you more than likely have a good mechanic helping you out. Be thankful for that 1st off.

I would look more to the fuel delivery. Filter, fuel pressure sheck, yadda, yadda, yadda. Lean means your not getting enough fuel. So there has to be something causing that. The sensors are telling you where to look. I have read your initial post and have seen nowhere you have changed the fuel filter or did a fuel pressure check. You may have a blockage in the filter.

Just my thoughts. I hope this helps a little. My book says to replace the fuel filter every 15k miles or every 12 months. That could be your hang up.

Good Luck MAN!

 

Thanks guys for the replies. I did change out the feul filter around 5k miles ago and had the injectors serviced as well. I'm starting to become convinced that this Ethanol revolution is causing all of these problems. This is my 3rd Ford and I have never had these problems before. I'm going to have to try and find the time to leave it with my guy and possibly rent a truck but works been slow and I don't really have the money right now. I'll keep you posted on what I find out down the road to help out the rest of the irritated with these issues.

 

The codes, no matter if they are 171/174/2195/2197, are all the same type reporting codes for excess air entering the intake system and sensor failures themselves.
All the hoses, cracks in the intake manifold, bolts loose, gasket sucked in, air entering the exhaust ahead of the OX sensors is all detected by the OX sensors and try to richen up fuel injected but can only go so far in corrections..
This goes to the point the motor runs rough from leaness in and not enough fuel to counter the leaness.
There are different procedures to use for leak detection. Some use propane, some use smoke, some use a scanner to watch certain sensor reactions to forced test procedures.
Go over air tube, the air meter, the throttle body and mountings.
Anything that attaches to the intake and could admit air.
Go over intake manifold to block bolts.
At idle, the IAC most likely closes down in responce to the 'outlaw' air in trying to get the idle to match the program value, so the converter loads the idle speed down such that the IAC won't correct for it and your giving throttle makes up for it.
After all this then it's time to get deeper into it or make a decision since you work out of the truck for a living.!
There is a time that your down time and money lost begins to add up to more than a decison on the truck or a backup.

 

You're right. Thanks for the info. I usually love challenges and problem solving. Not this time.......I will learn something, however, out of this and the knowledge is the key I guess I am a little concerned about long term damage by the time frame that it's taking to get it fixed. By the way, should the elbow on the PCV pull out so easily. I can literally pull it out with no effort and it doesn't seem to be seated or sealed at all. Could air get in that way. It's not cracked or anything. Just seems to be loose in the valve cover.

 

No, it should NOT be loose like that.

Can't blame it on ethanol - all fuel in the Chicago area has been 10% ethanol for at least 15 years now and they don't have any higher incidences of engine problems there than anywhere else in the country.

 

Ok, took off the IAC today to inspect. This one looks a little different from my '03. It has sort of an accordian type fins in the front and about half of the spring exposed on the other side. I cleaned it (Thought my mechanic did that) and it had alot of gum between the springs. Reset the SES and we'll see in the morning for the true test when i fire it up and let it warm up. After about 10 minutes, I will know if what it was doing was from the IAC being dirty. BTW, what's the typical life on one of those. The truck only has 50,000 and it's a 2004. Thanks

 

Hey guys, I'm new to the forums but have the exact same problem with my 2004 Heritage and was wondering if there was ever any closure to this issue. I cannot find any problems and have replaced all O2 sensors. Thanks, any help is appreciated

 

I would say post #6 was the problem.

 

Any 4.2 liter with a composite intake that's setting lean codes needs intake gaskets and isolator bolts for starters.

 

Hey, Helspen and others. We are in the middle of having the exact same problem. Have actually replaced the two O2 sensors, no change. Changed the fuel filter, no change. Then today I could hear a vacuum leak somewhere around the dust cover, so we are pulling the dust cover off to determine exactly where this leak is, if possible to tell. I will keep you posted on our findings. Unfortunately we discovered after buying and replacing the two O2 sensors that those codes cover such a pandora's box of issues and it isn't the sensors themselves. BTW, our local parts store put the reader on the truck free of charge to get the codes, they just couldn't give any info as to what those codes are specific to. Guessing it generally refers to vacuum/fuel issues.

 

That was exactly what I had to do. I also did the EGR valve. 6 months and 10000 miles later, it's running like new

 

OK, we never got a report as far as exactly what those codes mean other than they simply mean "running lean" and there is a problem somewhere. However, I did hear a leak under the dust cover, we removed the dust cover, got ether and sprayed in various places near each hose until we heard the engine rev up after one particular hose/area was sprayed. It was hose/part number 2L3E-6K817-BA 33011 M536F>PA6< that cost about $20, which we had to go to the dealer to purchase. It installs in the back behind the dust cover and all the other hoses, underneath where the hood separates and rounds down, a real bugger for big hands. A simple leak due to a worn-out hose. Now it is running top-notch again. It was a costly lesson for me to not look and listen first instead of listening to the parts store help, $160 that could have been used a lot wiser. I sure hope this helps someone else get this same problem solved quickly and painlessly.

 

Yep, the infamous PCV elbow. If you would have come here first, someone would have led you right to it.