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Discussion Starter #1
Early this month, the CEL came on in our 2010 EXL and the code pulled was P0171 (fuel system too lean bank 1). This code could be related to many things in the intake, fuel, evap systems from what I can tell. But my wife recalled that she had just fueled up one or two days prior, so she removed and tightened the gas cap even though there was no CHECK FUEL CAP message appearing. I didn't clear the code, but after the next three drive cycles, the CEL went away. Strange that we didn't get the fuel cap message, but with the code gone I wasn't worried.

A few days later after a roadtrip, we refuel the car again but no CEL appeared so all seemed fine. Two weeks go by and the CEL comes back on but this time there are two codes - P0171 again and it is joined now by P0174 (fuel system too lean bank 2). Ask my wife and she had just fueled up the car again two days earlier. Again there was no CHECK FUEL CAP warning. So I had her remove and retighten the cap this time and I cleared the codes. Several drive cycles since then and the CEL has not returned.

While I hope this is just a gas cap issue, I am now concerned that there is a minor intake, fuel or evap issue that is creeping up. Since there is no fuel cap message, perhaps it is just a coincidence that we are fueling up a day or two before the CEL comes back. I suppose the gas cap could be tight enough for the car not to sense it is loose (and give a CHECK FUEL CAP message) but maybe just loose enough to affect the air/fuel mix.

I will probably wait and see if this CEL keeps returning, but I wanted to post here in case anyone has had a similar issue with these codes and gas cap.
 

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First thing first: check the intake air duct for cracks.
 

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Discussion Starter #3
I checked the air duct from air filter to intake and did not note any cracking in ribbed section. Is that what you meant?
 

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It usually cracks around the throttle body side clamp. Look for a circular crack near the clamp.
 
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Discussion Starter #5
It usually cracks around the throttle body side clamp. Look for a circular crack near the clamp.
Thanks for the tip on where to look, and look what I found:
132671

close up

132672

wide view

I assume this is what you were talking about. So does this mean that extra air (dirty) is being pulled into the intake that is not being detected by the MAF? So then the oxygen sensors on the exhaust see more air than expected (lean condition) and increase fuel input to compensate which leads to a CEL?

Perhaps this crack might explain why this code keeps coming and going. I kind of ruled out the gas cap since the code returned and tightening the cap didn't make it go away after the next 4 drive cycles. Since then the codes have come and gone away intermittently.
 

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Discussion Starter #7
Yup, that. Great that you found it!
Yeah, if @can hadn't been so specific, I am not sure I would have looked in that exact spot.

Problem is it will be several days before I can get the part and replace it. I wonder if I should put some duct tape over the crack for now. At least then dirty air won't get in for now. Bad idea?
 

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Discussion Starter #9
LOL, your decision flowchart makes it easier. I figured it is an air duct after all so duct tape seems appropriate. Same concept just a much hotter environment.
 

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Discussion Starter #10
Ordered Tube, Air Flow - Honda (17228-RN0-A00) this morning. Online parts sites wanted $27 plus about $11 for shipping. Local dealers wanted $38-45 plus tax to special order so I went with the aftermarket Dorman 696-138 Engine Air Intake Hose for $35 plus tax from Amazon. The upside of Amazon is that I have a chance to get the part before this weekend. The upside of the aftermarket Dorman is that it comes with the fasteners in place and also the clip for the air bleed tube which I discovered is missing on mine (see pics above and below). Didn't realize until I watched an install video that the clip on mine was missing. It's a mystery to me why that was removed but perhaps long ago someone (not me) had to remove the air bleed tube and did a poor job reinstalling it.

In the meantime, I attempted to cover the crack with duct tape but it was tough given the dirt on the tubing already and the nooks and crannies make it hard to get the tape into place. An F for aesthetics, but if it helps who cares.
132678
 

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Dorman from RA will be my next duct as the 2nd Honda duct has started to develop cracks on mine.
 

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Discussion Starter #12
RA has it for $20 which is a great deal, but I wanted to get to this weekend so I see if these codes return or not. With expedited shipping it was more than Amazon. However, if I could wait then the cheapest shipping was $8.
 

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Dorman from RA will be my next duct as the 2nd Honda duct has started to develop cracks on mine.
It was out of stock for a 2006 when you wrote that, so I signed up for a notification when it would be back in stock again for you. Just got it now, and they only have one. Grab it!

 

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Done, thanks!
 

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Discussion Starter #16
With the duct tape installed for the last 9 days, the lean CEL codes did not return. So one could conclude that tear/crack in the tube was the cause. Time will tell...

Today, I finally had the chance to install the Dorman air flow tube. Install was straight forward and it saves time that the clamps are already on the tube and lined up. I found it easier to stand on the driver side and remove the air filter box and work my way towards the throttle body removing the cables, clamps, and breather tube. In addition to the alignment notches on the top of both ends, there are ridges inside the tube that act as stops for the throttle body and air filter cover. That way you can look inside with a flashlight and see if the tube is flush with the ridge all the way around.

After removing the old air flow tube, I noted that the tear covered about half of the circumference (from about 4 o'clock to 10 o'clock looking in from the throttle body opening). I expect this part of the tube gets stressed when the air filter box is lifted. Despite my best efforts, the tear was only partially covered by the duct tape so I am glad I finally got around to replacing it.
 
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