Solution to my Code P0171, P0174 Problem
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New User
Joined: Nov 2011
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From: Surrey BC, Canada
Solution to my Code P0171, P0174 Problem
On a long trip in our 2013 E350 Class C motorhome (6.8L V10) I had the notorious CEL accompanied by rough idle and stalling. Long story short, I pulled the codes with my Autel unit and found the P0171, P0174 codes indicating lean condition on banks 1 and 2.
After searching the forum I understood that this was most likely an air leak after the MAF, somewhere near the throttle body. I looked at the usual suspects: PCV valve and hose, intake rubber boot etc but all looked good. I started the engine and tried the carb cleaner spray around the the throttle body without finding anything.
Fortunately, while doing this test I did hear a hissing noise that sounded suspicious. I couldn't locate it from the front of the engine bay so I went into the cab and removed the dog house to get at the rear of the engine. The air hiss was twice as loud at the back so I knew I was onto something. I ran my hand around the throttle body and at one area the noise stopped. My finger had covered a small hole in a rubber plug over an unused tube. As soon as I covered it the idle smoothed out and the engine was as smooth as silk.
I have attached two pictures that show the location of the air tube. The first shows the general location on the rear of the engine (from the cab side) and the second shows the actual tube cover with the hole in it.
I have no idea what could have caused this hole other than just heat deterioration. It is not near anything that could have caused abrasion.
Anyway, if you are chasing a phantom vacuum leak, I hope this helps!
After searching the forum I understood that this was most likely an air leak after the MAF, somewhere near the throttle body. I looked at the usual suspects: PCV valve and hose, intake rubber boot etc but all looked good. I started the engine and tried the carb cleaner spray around the the throttle body without finding anything.
Fortunately, while doing this test I did hear a hissing noise that sounded suspicious. I couldn't locate it from the front of the engine bay so I went into the cab and removed the dog house to get at the rear of the engine. The air hiss was twice as loud at the back so I knew I was onto something. I ran my hand around the throttle body and at one area the noise stopped. My finger had covered a small hole in a rubber plug over an unused tube. As soon as I covered it the idle smoothed out and the engine was as smooth as silk.
I have attached two pictures that show the location of the air tube. The first shows the general location on the rear of the engine (from the cab side) and the second shows the actual tube cover with the hole in it.
I have no idea what could have caused this hole other than just heat deterioration. It is not near anything that could have caused abrasion.
Anyway, if you are chasing a phantom vacuum leak, I hope this helps!
Cargo Master
Joined: Apr 2013
Posts: 3,087
Likes: 24
From: Central Florida
Looks like a hose broke off there. Am I wrong? You should look around under there for a hose that’s not hooked up to anything.
also my v10 doesn’t have either of those ports. Maybe they are aftermarket..?
also my v10 doesn’t have either of those ports. Maybe they are aftermarket..?
Thread Starter
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New User
Joined: Nov 2011
Posts: 4
Likes: 0
From: Surrey BC, Canada
No, definitely just a rubber cap over the end of an unused port. Hard to see in the photo but only half of the end of the rubber cap was missing. There is no "mystery hose" flopping around!
Also, this is a 100% stock 2013 engine in a Sunseeker Class C motorhome, so original TB and intake. I'm assuming this is just an unused vacuum port.
JG
Also, this is a 100% stock 2013 engine in a Sunseeker Class C motorhome, so original TB and intake. I'm assuming this is just an unused vacuum port.
JG
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