04 4.0 Bank 1 and 2 lean

[jbizub5192]

Hi everyone, I am having the bank 1 and 2 lean codes coming up on my 04 ford explorer 4.0. I have 255k on the explorer. I know the older generations had major issues with the intake gaskets leaking(both lower and upper). I cant seem to find much info on the newer generation 4.0 that is used in 04 explorer. I have already replaced both upstream o2 sensors hoping that would fix it. It did not but wasn't a totally waste because it was due for new ones anyways. Does this sound like a leaking intake gasket? My lt fuel trim in around 22 when I think its supposed to around 5 tops. It is dumping fuel like crazy because im getting 14.5 on the highway. Thanks for the help!

 

[jbizub5192]

any ideas? thanks

 

[2000StreetRod]

cruise vs idle LTFT?

Usually leaking intake manifold gaskets have a much greater impact on AFR at idle than cruise. Have you checked your LTFTs at cruise?

Have you measured your fuel pressure? I can't remember if there is even a Schrader valve on the 2004 for testing fuel pressure. As I recall you have a fuel pressure sensor on the fuel rail and a fuel pump controller to maintain a specific fuel pressure. The fuel pressure sensors are not real reliable and could be reporting an incorrect reading to the PCM.

 

[jbizub5192]

The ltft is just an average of the short term right? If thats the case than the average is calculated overtime so in the end when i view the data for ltft at idle it already has stored the values when it was on the highway. I have checked it while moving and it still was the same high result. Why would fuel pressure be the issue? It is certainly getting enough fuel(too much actually because the ltft is over 20 which means it is dumping fuel like crazy). I know it is because my millage is crap now lol. Thanks for the help

 

[2000StreetRod]

Stft & ltft

When the STFT exceeds a certain limit rich or lean the PCM adjusts the LTFT to get the STFT near 0. What were the actual DTCs? Is the LTFT +20 or -20?

The PCM controls the duty cycle of the fuel pump to maintain a specified fuel pressure (around 40 psi as I recall) as measured on the fuel rail by the fuel pressure sensor (FPS). If the FPS erroneously outputs 30 psi when the actual pressure is 40 psi the PCM will increase the duty cycle of the fuel pump to bring the measured pressure up to 40 psi which could be 50 psi actual. if the FPS erroneously outputs 50 psi when the actual is 40 psi the PCM will decrease the fuel pump duty cycle to bring the measured pressure down to 40 psi which could be 30 psi actual. The O2 sensors would sense a lean condition and the PCM would richen the AFR to bring it back up to normal.

Have you recently installed a new aftermarket oiled cone air filter or recently cleaned and re-oiled an existing one? If so, the oil can contaminate the MAF sensor and cause inaccurate readings.

 

[ExcursionMJ]

Do you have a P0171 and a P0174? If so you're most likely looking at a bad mass air flow sensor. When you get both of those at the same time it's almost always an issue with the MAF or IAC.

 

[jbizub5192]

Just for any update, today I replaced my intake gaskets as well as the pcv valve plus its hose that connects to the intake. My ltft for bank 1 and 2 are now both exactly +25. Before Bank 2 was +23 and Bank 1 was +16. I am now think being though these numbers are identical it may be the MAF like you all said. I only drove it about 30 miles so far so I know it hasn't completely leaned yet. I do aftermarket filter that I recently oiled. Last week when this all started I used one of the special MAF sensor cleaner sprays but that didn't do anything. Im guessing my next thing to try is the MAF sensor. I tried to do the low cost option first but that didn't seem to work lol.

thanks for the help!!
ps. I did have the battery disconnected for a while so everything reset.

 

[jbizub5192]

I put the new MAF sensor in and my ltft did not change a bit. (I disconnected my battery so everything is reset). The values are identical to before. At idle my ltft is +25, when driving the ltft is also +25 it goes down to 23 with a change in terrain but then climbs right back to +25. When driving my stft is close to zero with minor fluctuations (+5 , -5 ish). However as soon as i let off the throttle it jumps to the 25+ range. What does the problem seem like? Still a vacuum leak or that pressure sensor you were taking about? thanks for the help!

 

[2000StreetRod]

idle vs cruise LTFTs

Since your idle LTFTs are not significantly different from your cruise LTFTs I doubt that the problem is a leaking intake manifold gasket. Intake manifold gaskets leaks are small and vary with vacuum, not airflow. If you do have a vacuum leak, it increases as airflow increases causing the fuel trim to remain fairly constant. Check the bends and undersides of vacuum hoses for splits. Look closely at the PCV valve hoses. Ford went to electronic throttle control in 2004 so you probably don't have an IAC valve to check the hoses to/from. Make sure the EGR valve is on tight and check the condition of its gasket. Check the vacuum hose to the EGR vacuum regulator (EVR) and from the EVR to the EGR valve.

Besides checking for vacuum leaks I suggest measuring the fuel pressure. Hopefully, Ford did not delete the Schrader valve on the fuel rail in 2004 when the fuel pressure sensor was added.

Edit: Do you still have the hose connecting the main intake hose to the passenger side valve cover? Some members delete the hose and install a breather when adding an aftermarket intake. That allows unmetered air to enter the intake system causing a lean condition.

 

[D Hook]

LTFT = ?

STFT = ?

The rest is understandable but these two have me baffled.

And how does one go about checking them?

 

[jbizub5192]

I have already checked all of the hoses and they look in good shape. I did replace the pcv valve hose because it looked like it could have been bad. I think my next thing is to rig up one of the diy smoke test machines to hopefully see where / if there is a leak. Where would the fuel test port be. I think they might have done away with it because I don't recall seeing it by the rail. If this is the cause how do I check the pressure? I also did not install an aftermarket breather by the valve cover like (wish it was the easy lol). Even though the ltft is +25 it still runs great, you would never know there was a problem. I mean at times it could be smoother at idle but that is expected at over 250k. Thanks for all of the help!!

 

[jbizub5192]

Do you think A smoke test should be my next step? How do I test the fuel pressure if I dont have a test port. thanks

 

[2000StreetRod]

no Schrader valve

I was afraid that Ford deleted the Schrader valve when the fuel pressure sensor was installed. You may be able to read the fuel pressure via the OBD-II port with the same device you're reading the fuel trims.

Are there any other diagnostic trouble codes besides P0171 and P0174?

 

[jbizub5192]

If I recall I think I do remember seeing the pressure listed in the menus. I think it was around 39. I will have to double check that though. Those are the only codes for the engine. I have a trans code about the pressure solenoid ( really it is a servo bore leak). But this code would have nothing to do with the engine itself. Thanks for the help

 

[2000StreetRod]

determining fuel economy

You posted that your fuel economy was 14.5 mpg on the highway. I assume that was based on PCM computations. Have you actually calculated your mpg using miles driven from full tank to full tank? The PCM calculates mpg based on injector pulse width, fuel pressure and injector characteristics. If the fuel pressure is being sensed incorrectly the calculation will be inaccurate. That might be a way to indirectly check the fuel pressure.

 

[jbizub5192]

Unfortunately I don't have the on-board mpg display. So I did it the old fashion manually way by calculating it out.

 

[2000StreetRod]

fairly accurate mpg

So that means that your computed mpg is fairly accurate and that for some reason the pre-cat O2 sensors are sensing a lean condition but the AFR is actually rich. The O2 sensors don't actually measure the AFR, they just compare the O2 level to atmospheric. So if fuel doesn't burn and consume the oxygen the level measured by the sensor will be greater than normal. Normally, that would result in misfire codes. The PCM computes the power output of each combustion and sets a code when one cylinder varies significantly from the others. However, if all cylinders have uniformly low power typically the PCM will not set a code.

I suggest performing a compression test to see if it is low. If normal, then start searching for sources of excess fuel. I doubt that you have an intake leak.

Is the engine, intake and exhaust still in the stock configuration?

 

[jbizub5192]

Yep everything is all stock. I will check the compression. The only reason why I thought it may be an intake leak is because after I replaced the intake gasket my fuel trims went from bank 1 15% bank 2 23 % to bank 1 25% bank 2 25%. Both numbers increased. I thought maybe it had a previous leak but then by moving it around when taking it off the crack could have gotten worse since my fuel trims actually got worse rather than better.

 

[Berky]

Do you have a P0171 and a P0174? If so you're most likely looking at a bad mass air flow sensor. When you get both of those at the same time it's almost always an issue with the MAF or IAC.

I have both 171 and 174. I replaced the fuel filter, cleaned the MAF. Still have them. What should I go to next?

 

[Berky]

What's an IAC?