Okay guys, I pretty new to this forum but I'm hoping that someone on here has some kinda answers for me.

I just purchased a 2003 F250 Super Duty with the 6.8L V10 It has really high miles on it as it was a landscaping companies fleet truck. I'm sure that it was pretty well serviced as it has 300K miles on it and it's still running pretty decent.

I picked up the truck for a steal for $1200 and I have to get the smog done soon thanks to glorious CA state law.

It idles with what I can only describe as a slight miss and it runs and drives great. seems to have plenty of power for the miles that's on it.

There is no active CEL on but I scanned the OBDII system and found a P0171 Lean bank 1 code in the pending codes list of the scanner.

I guess this year engine doesn't have an EGR Valve or DPFE sensor because I've looked high and low for it and there non existent on this engine.

I've checked for vacuum leaks by spraying brake cleaner or carb cleaner all over the place and it makes no difference and all the vacuum lines and connections look okay.

When it's running It does sound like a vacuum leak right behind the top of the plastic throttle body but I can't find it, I don't know if this big *** engine just sucks that much air or what.

Like I said I need to smog this thing soon and I don't want it to fail if it's missing or has another issue.

Any help would be very appreciated.

Thanks in advance

Oh the fuel injectors look new and one coil pack looks like it's a replacement

 

Check out this video, there is a PCV elbow that can crack or dry out.

 

Had the same code on mine at one time and it was the pvc hose on drivers side valve cover that was cracked right where it went into the valve cover

 

Pretty common issue on these trucks.

Keep in mind, once you've cleared the code, After fixing the vacuum leak, you need to run it through a variety of cycles before the smog check. This includes at least 5-6 on/off cycles, Frwy driving, start and stop, 35 mph runs, etc to clear that pending code.

If it hasn't cleared properly, the tech can't do the test, but he will charge you for it.

Remember, here in CA, they can't ask questions. The best thing to do is tell them that it has been worked on recently and to check for codes PRIOR to the test. If it still prompts, they won't run the test nor charge you for it. Just drive it some more.

 

I checked the pcv hose and it looks fine i removed it and twisted it all around and its not brittle and doesnt have any cracks ....would a bad pcv valve itself cause this issue? When i remove the pcv and put my finger over it the pcv sucks down like it should but when i put it back into the valve cover i cant here or feel it suck closed....or am i not supposed to? I checked all of the rubber hoses and vacuum lines and they all look good .......this year v10 has some kind of electronic egr and no dpfe sensor so that cant be it....what about the egr vacuum thing that on the firewall dont know the name but it looks like it has a removable lid/cap on top but its not actually removable and its got 1 vac line and 1 electrical plug on it and on the side has a saucer looking thing like an egr valve

 

The pcv valve and hose right off the PCM won't usually go bad and create the problem. Your PCM valve is simple a metal valve with a check ball, preventing two way flow. It's easy to clean and usually, the pcv elbow further back on the pass side is thin rubber that cracks easy.
If you can't find a leak, check for a dirty MAF sensor, helping to create a lean condition.

 

Yeah I'll buy some MAF cleaner tomorrow and spray that out and see if that helps at all. This engine only has one PCV valve on the passenger side valve cover, the driver side doesn't have a PCV valve in it, it has a hose connected to it that goes from the valve cover to the air cleaner tube right before the throttle body. I can try and upload pics tomorrow.

Is this V10 Supposed to have 2 PCV valves on it? If so that may be one of my issues lol


Thanks for all the help

 

Only one PCV valve.

 

When you have the air filter out to look at the MAF sensor check the rubber grommet on the bottom of the air filter assembly for the wires, it isn't uncommon for it to pop out and let unmetered/unfiltered air into the intake and cause a lean code and a ruff idle.

 

Okay so I sprayed the crap out of the MAF sensor with electrical parts cleaner from the parts store, and it didn't improve anything.

I plugged my scan tool in and read the fuel trims % @2500 RPM

STFT1 and STFT 2 were bouncing around from -1.6 to about +6.3

But:

LTFT1 was at about +6 so that is lean
LTFT2 was at about -7 So that's rich

How the hell am I getting a rich and a lean condition at the same time from head to head?

I'm starting to get frustrated with this truck

Does anyone have a good place to start? Preferably from cheapest to most expensive lol

This is what I have gathered from stuff online, but where the hell do I start there's gotta be some kind of order of operations here so I'm not wasting my time doing redundant things........



Some possible causes of LEAN fuel mixtures include:

Air or vacuum leaks in the intake manifold, near the throttle body or at vacuum hose connections.

Weak fuel pump that is not generating enough pressure or volume

Fuel line restrictions (like a pinches hose or plugged filter)

A weak fuel pressure regulator that is not maintaining adequate fuel pressure

Air leaks in the PCV plumbing

Dirty MAF (Mass Airflow) sensor that is under reading airflow into the engine

Dirty or dead fuel injectors

Ignition misfire (a fouled spark plug, weak ignition coil or bad plug wire that causes a misfire allows unburned oxygen to pass into the exhaust and fool the O2 sensors)

Compression leaks (bad exhaust valve that allows unburned oxygen into exhaust and fools O2 sensors)

Exhaust manifold crack or gasket leak (allows unburned air into exhaust and fools O2 sensors)

Bad O2 sensor (signal shorted to ground so the sensor reads lean all the time)



Some possible causes of RICH fuel mixtures include:

Leaky fuel injector

Excessive fuel pressure due to bad fuel pressure regulator or restricted fuel return line

Extremely dirty air filter or restrictions in air intake system

Exhaust restrictions (clogged converter, crushed exhaust pipe or plugged muffler)

Bad O2 sensor (output shorted to voltage so it reads RICH all the time)

Thanks in advance guys.......




Okay so now I went back outside and checked some more readings on the scan tool

The MAF reading was at 0.02 is that right?

Also the 02 Sensor after the CAT is reading 0.95 volts and this is indicating a rich condition.....Right?

How is it that I had a pending code for Bank 1 Lean but the overall outcome is a rich reading on the 2nd 02 sensor?



Lean on Bank 1 ...Rich on Bank 2....??????? No wonder this thing idles funny lol ........

HELP!!!!!!!!!!!!!!

 

With that v-10, a failing cop won't be as obvious as a 6 or 8 cylinder.
Most of the time it's a failed cop, then a possible plug, and last... Poor compression.
If the first, pre cat, o2 sensor reads lean and the post cat reads rich, the two sensors compare reading to determine the cat's effectiveness.
Since it shows on bank one, I'd go back and pull each cop on the passenger (bank 1) side and look for rusty springs or boot cracks.

 

Actually, your fuel trim readings are OK and not at all unusual. If the long term and short trim (mathematically) combine to equal less than 10% (on each bank), it is usually not a real problem. While close to zero is ideal, it is not "normal" to see zero fuel trim readings. Also, you can check the fuel trims at idle and compare that to fuel trims at about 2500 RPM. If the fuel trim at 2500 rpm gets better (closer to 0), you likely have a vacuum leak. If the fuel trim at 2500 rpm gets worse, you likely have a MAF problem or a fuel delivery problem.

Your symptom still acts like either a MAF issue or a vacuum leak issue. I am not sure what all that you have checked, but you cannot check some of the vacuum lines without removing them. Don't forget the intake manifold and the brake booster.

You may need to do a little more research to see what "Normal" is.

Testing the cops and other components requires further discussion.

 

I took off and inspected all of the C.O.P's and they all visually looked really good I'm pretty sure the previous owner replaced all the C.O.P's and all the fuel injectors because they all look really good. The previous owner was probably chasing the same problem I am.

Because the mileage on this beast is so high 310,000 I'm starting to think maybe it has bad compression or something more major, I hope that's not the case though.

Which vacuum lines do you need to remove to properly inspect? In the video that's posted in one of the replies on here it looks like the guy pulls a rubber hose out from under the throttle body but I don't have any hoses under there.

I sprayed a whole can of brake cleaner all around and all over the throttle body area, intake manifold vacuum lines etc with no variation in the idle at all.

To me I still here what sounds like the engine sucking a lot of air from right in front of the IAT but I've rubbed my hand all up and around in that area and can't find any cracks or anything even with the brake spray.

How fragile are the spark plug threads in the aluminum head? I've been real reluctant to pull any of the plugs knowing that lots of people had issues with cross threading and having blow outs.

Anyone know how to test the C.O.P's with a DVOM?

 

Some 03's have the extra thread length in the spark plug holes, some don't. My dads 03' was an earlier build date (built in 2012) and it did not have the extra thread length. I always did the plug changes for him without issue. But you never know what kind of mechanic could have worked on a used truck and what damage they may have done. If it were me I'd pull the plugs and changing them is cheap. If the plugs are worn or a plug is bad it could cause your code. I have gotten the P0171 code already from some detonation.

 

The build date on mine is later in the year like October or November so maybe it's got the longer threads......

Anyone want to buy this truck from me? I got about $1,400 into it I got all needed DMV paperwork to get a title.......Needs SMOG and Brake and lamp inspection to get new Salvage title.......

I'm in Sacramento CA, hit me up if interested at all