P0171 P0174 CEL with headers. Ignore?

[Fantasymon]

I have the following two codes:
P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

I have searched on here a lot but I think my situation is a little unique. I have the KKM air filter, BBK throttle body, and then BBK headers. I had some maintenance guys replace my head gaskets and a bunch of other stuff including installing the headers.

I now get the two codes. They changed all of my 02 sensors. When I took it back to them they said that it is because the headers allow so much extra air through the exhaust that it is causing the system to run lean and make the codes to trigger. They said the only way to fix it would be to buy some expensive high performance 02 sensors. They said that I should just ignore it. (I bought all of the parts myself so its not like they were trying to sell me some expensive parts).

I do trust their knowledge for the most part but I still don't like the idea of the check engine light being on due to the system being too lean.

Should I take their advice and just ignore it? I have also done a performance tune several years ago from the guy on here (forgot his name).

 

[Fantasymon]

Well I think I fixed the problem tonight. I replaced the 10 year old KKM filter with the K&N FIPK kit and I cleaned the MAF sensor with MAF cleaner. Just drove about 10 miles accelerating pretty hard and the check engine light didn't come on. Hopefully this fixed the problem and gets me a little better MPG!

 

[DAMN]

Most common problem for that would be an exhaust leak...short term blm's on the o2's read the extra air as a lean condition and dump fuel until it runs pig rich. Headers and intake will not cause your vehicle to run so lean that it would throw a code...remember your ecu in the vehicle can compensate a small amount for mods done to the it just not anything like ported heads or camshafts.

 

[Fantasymon]

NO!!!! After driving about 10 miles today, the check engine light came back on. Same P0171 and P0174 codes. UGH!

After searching on here it looks like the fuel pump could be another possibility but I'm not about to have that changed without doing some testing on it.

How can you diagnose an exhaust leak?

What is the ultimate downfall of these codes if it is an exhaust leak....just lower mpg?

Everything seems to run fine.

 

[gmanpaint]

http://www.aa1car.com/library/ford_lean_codes.htm

Good write up there for your codes.

I'm going to say you need that tune updated for the headers.

 

[DAMN]

First stop guessing what is wrong with it....Its not your fuel pump so do not bother. You have a lean condition on both banks of your engine which is probably being caused by your header gaskets leaking or where your headers bolt to your exhaust is leaking. Its a very common problem for people who do header swaps. Worst case is your ecu is going to read that your o2's are reading a lean mixture probably being caused by an exhaust leak and its going to increase your fuel injector pulse width to try to richen the mixture back to stoich 14.7/1 but its never going to reach that so its going to max out your blm's which is going to cause your vehicle to run hella rich and your mileage is going to suck and its prob going to kill your cats and o2 sensors. A tune will not fix this.


You can try to find the leak by listening for any tisk tisk tisk or tapping sounds coming from your engine bay more notably from your header area's. i would check all your header bolts because they back out after you install new headers and need to be tightened up after a few heat cycles.

 

[ranger7ltr]

What is your fuel pressure? Age and condition of the fuel filter? Vacuum hoses?

The fuel pressure can definitely cause a lean condition especially if it is lower than spec. On your truck you should have a minimum of 55 psi with the proper operating range of 65-72 psi...

When did you last change the fuel filter? These trucks get really touchy about their fuel being delivered at correct volume and pressure...

Just remember that any system that is part of your trucks' management systems can cause numerous issues...A vacuum leak can cause a lean condition... An exhaust leak can also do that as well as not enough fuel to the injection system...Your EGR system can cause the lean condition as well.. Plus you have both banks being lean so the problem is affecting both sides of the engine...And I would hope you could hear exhaust leaks on both banks of the engine if an exhaust leak were causing this issue...

What engine are you running? An intake leak can do this as well..Never discount any system when investigating error codes... Any or a combination of more than one area can be a problem needing corection.

And also don't discount the fuel management system and its ability to compensate for changes in the running condition it monitors...That is a major part of its design; to compensate for changes in the running conditions it monitors...Since these trucks run a MAF system, different flow characteristics caused by heads, cams, bigger valves, cylinder volume,exhaust breathing, etc will be monitored and compensated for to a point... It is when going past the point of compensation that a tune is needed to change the range of monitoring the PCM will do before throwing an error code.

 

[Turdle]

The headers are not the cause of this issue which should defnitely not be ignored. It is also not a tuning issue, as the PCM will easily make up for the headers.

If you had an injector problem I am almost certain you would also have a misfire code.

I say there is a vacuum leak somewhere. What is the condition of the egr tube? Have you double checked all vacuum lines? quadruple check the pcv valve and the grommet, and, also the vacuum feed to the fuel pressure regulator

I am not a fan of converting a air box to a direct element, as this disrupts the airflow upstream of the maf sensor-causing these type of issues.Maf sensors are calibrated to box type or cone element filters. Changing anything upstream of the maf is not a good idea, without a datalog and re write of the tune file.



Stick all the stock stuff back on, clear the codes and see what happens.

 

[gmanpaint]

When I had a lean code on both banks it was in fact a blown intake manifold gasket. Was very hard to figure out, because it was a very small leak, but was enough to cause havoc.

 

[DAMN]

Too bad he doesn't have datamaster and can run a short datalog it would tell us whats going on.


I don't think its a fuel pump or filter issue because it ran fine before all the work was done. My money is there is un-metered air entering the exhaust side of the engine somewhere if it was entering the intake side it would cause the engine to rough idle but wouldn't cause both banks to run so lean it throws a code. I wish you could monitor what your front o2 sensor are reading. On the cars i have tuned that had a bad fpr the car misfired slightly and didn't rev normal.

 

[Fantasymon]

Thanks for info guys. The check engine light was actually on before they did the work and it is was initiated me to have my car checked out. I took it to a local repair shop that "specializes in Fords" and they said my head gasket was leaking, camshaft position assembly was bad (car was squeaking), and several other issues. They wanted a ton of money to fix everything ($1600 for the head gasket replacement alone) and I couldn't justify it since the car is 11 years old.

I found some local mechanics who agreed to do the work for much cheaper as long as I buy all of the parts myself. They pulled the codes and said it was one of the 02 sensors but I didn't write down the code(s) then. Stupid I know.

I had bought the headers about 3 years ago off of somebody on here but never got around to installing them. Since they were going so far into the engine, they agreed to install them for $75. Unfortunately there were some issues with the connections and they had to take it to a local muffler shop to do some special welding. I am not really familiar with what the EGR valve does but they mentioned it several times when talking about the headers y pipe not connecting correctly which the muffler shop fixed.

I asked them if these are the same codes the explorer was pulling before and the mechanics said no.

I am far from a mechanic and don't really know how to check most of the stuff you guys mentioned above.

Also, the explorer idles as about 1500 RPM. After doing some searching on here, I am guessing this is from the BBK throttle body. I may try to clean the IAC but I don't think this is a function of these codes.

 

[joecrna]

Don't continue to drive a lean vehicle.

If I understand correctly, you now have a K&N fresh air intake and filter, BBK Throttle body and BBK headers. These should not cause the lean condition you originally mentioned in the first post codes. The BBK throttle body may cause some drivability issues whithout a reprogramming of the computer but not a lean condition. Air is most likely entering somewhere. Everyone wants to replace O2 sensors because they don't really understand them very well. They simply don't fail all that often.

Now the question is, where is the unmetered air entering. Could be intake side or exhaust side of combustion chamber. Cleaning the MAF sensor was a good idea, only clean with fluid designed for this not carb cleaner.

An easy way to help find an exhaust leak; Get some "Sea Foam" cleaner and let the engine draw it in as you normally would per can instructions. It smokes real well. While smoke is rolling out the tail pipe, look at the rest of the exhaust for leaks. The smoke comes right out at any leaks most of the time. In your case you should be primarily looking ahead of the O2 sensors (both of them) and where the headers attach to the heads. This is a common leak point, maybe they just need retightened or the gaskets need replacement. Frequently header flanges are very difficult to seal.

Now the intake side. Im not saying you should do this of coarse but I have. You can spray various parts of the intake with carb cleaner or (much more dangerously) starting fluid. If an intake gasket or any part of the intake tract after the MAF sensor has a vaccum leak the engine will stumble or stall when the carb cleaner is sucked in at the leak. If "I" used starting fluid the engine will race when I spray the leak. Just got to be careful not to let the aircleaner draw in the spray or the engine will respond the same. I only use the starting fluid when I am extremely frustrated as this is an extreme fire hazard. I have done it though with good results. Also, for minor intake vaccum leaks Permatex makes a spray on gasket that will seal temporarily. I've done this at the track. It doesn't last too long but enough to finish the day.

 

[Fantasymon]

Thanks....I may try the sea foam idea soon. I don't think I will take the chance of the carb cleaner or starting fluid. I don't work on cars much at all so that makes me too nervous. I ran sea foam several years ago once so I am somewhat familiar with how to do it.

You are correct in my setup of K&N filter air intake, bbk tb, and bbk headers. Before last week, I had the KKM filter, factory intake hose, bbk tb, and no headers. The tune I have was setup for the KKM and the BBK tb several years ago. I replaced the KKM with the K&N filter and piping because the KKM was 10 years old and I had only cleaned it a few times. The factory piping was also having some issues so I just decided to replace with the complete K&N intake kit.

In terms of the computer, I don't think there is much difference between the KKM and the K&N. So really the only thing new that the tune would not know about is the headers.

 

[joecrna]

These small changes are well within the computers parameters and should not need a differnet tune (computer flash) to begin with. With the limited information we have so far, I believe you have a vaccum leak. The carb cleaner is not a fire hazard, it just needs a larger vaccum leak to produce a noticable stumble in the idle. However, if you aren't comfortable doing this you should find someone (mechanic ect) to help find the problem. Possible issues from driving when the computer senses lean; fried O2 sensors, burnt up catalitic converters, low power, poor drivability, bad fuel mileage and predetonation (ping) and the ensuing internal engine damage that could result. Any or all of these things could happen based on where the leak is, how bad it is, and what the computer does to try an compensate.

 

[Fantasymon]

If you are trying to scare me, then you are doing a good job! Just kidding.
Yea I agree that I need to fix the problem asap. Luckily I only have a 2 mile commute to work so I don't drive it that much. I can't just stop driving it as it is my only means of transportation.

I'm going to ask a dumb question, but what or where would a vacuum leak be at? Where are vacuum lines (is this before or after the engine). I assume this is completely different than an exhaust leak as exhaust is outward pressure and vacuum in a sucking in pressure.

 

[Fantasymon]

Well I looked around the throttle body area and I noticed what appears to be a disconnected vacuum line! Here is a picture. What does this connect to? I have a 2000 4.0 ohv.


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This second picture is a closeup of my BBK throttle body. Is this hole supposed to be there? It has threads for a screw but nothing is there. Seems like UN-metered air could easily enter there, but it may be designed that way??



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EDIT:
Okay after looking around some more, I think I figured out that this vacuum line is supposed to connect to my throttle body and came loose. Can someone please verify that this is where is goes? (see picute below) I am 99% sure but just want to be safe. Secondly, I tried to connect it but could not get it on. The diameter of the nipple on the throttle body is much smaller than the inside diameter of the vacuum line so it wouldn't stay on. Suggestions?



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Thanks!!!!

 

[ranger7ltr]

I think you found your lean code source...

The BBK tb has a nipple in the same place the stock tb does only it is smaller...The hose is the stock vacuum line going to the Evap purge valve under the battery...You will need to step the nipple size up to the correct size to make the hose fit tightly...

And the bolt hole is for the plactic cover that the stock tb used to cover the throttle cable and the cruise control cable...

Fix that vacuum leak and I'll bet the idle drops back to normal and the lean codes go away...Who knows the gas mileage might even go up too...

 

[Fantasymon]

Where would I find the correct piece to "step the nipple size to the correct size to make the hose fit tightly"?
Would this be at an auto parts store?
EDITED: I went to Advanced Auto and bought a 1/2 foot long 7/32" vacuum hose line. One end fit perfectly over the BBK nipple, the other end squeezed perfectly inside my current hose. I cleared my codes and now just hoping they don't come back on! This did not fix my idle problem, but I think/hope I just need to disconnect and clean the IAC to fix this.


I don't have the plastic cover. Any idea where I could buy one?
EDITED: I still need to find this cover or a screw that I can fill this hole with.

 

[Fantasymon]

bump....Anybody know where I can find that throttle body cover or know what size screw it is?

 

[gmanpaint]

bump....Anybody know where I can find that throttle body cover or know what size screw it is?

Have you been to the Junk Yards already? The screws (yes more than one) will come with the one you remove.

You can run without it, and I wouldn't stress over it.