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Hi all,
I have been following these forums for awhile but never posted. I have a 4.6L 2003 F150 that just turned 200k. It's running strong but is having some idling issues and sucking gas like crazy, I also noticed its started to backfire through the intake. I have taken it to a few mechanics but no one has really been able to help me. I replaced the IAC valve but still have issues with a high idle as well as fluctuating idle at times. I was told that I had a leaking hose which was contributing to the issue, it's the one I circled in the attached picture. I just have no idea what that hose is called so I can buy a new one to replace it. Any help would be appreciated!
A high failure item on a 4.6 is the PCV vacuum hose. Follow the hose from the PCV valve to the back of the intake. The elbow at the intake rots and cracks, causing a major vacuum leak.
Yes, I forgot to mention a mechanic removed the original and replaced it with what you see now secondary to a leak being found, although I was told by another mechanic that the new fabricated house is also leaking. I'm wondering if I bought a replacement through Air Raid if it would solve all my problems
Why not do this right and look at the long term fuel trims for being to far out of normal range.
They will tell you if there is an Intake air leak so you can be sure.
A leak at the exhaust header flanges to pipes can take in air will cause the same shift because the Ox snsors are down the pipe about 6 inches and will detect a leak.
An air leak is detected by the OX sensors.
If too much Ox is detected in the exhaust, they cause the fuel tables to shift rich.
This upsets Idle, causes roughness, stalling and poor gas mileage.
Your shops are not very good at diagnostics.
Also check the after market air Intake for proper install of all the hoses.
Good luck.
Why not do this right and look at the long term fuel trims for being to far out of normal range.
They will tell you if there is an Intake air leak so you can be sure.
A leak at the exhaust header flanges to pipes can take in air will cause the same shift because the Ox snsors are down the pipe about 6 inches and will detect a leak.
An air leak is detected by the OX sensors.
If too much Ox is detected in the exhaust, they cause the fuel tables to shift rich.
This upsets Idle, causes roughness, stalling and poor gas mileage.
Your shops are not very good at diagnostics.
Also check the after market air Intake for proper install of all the hoses.
Good luck.
Thanks, I will try this route as well. And yes, Ive been very frustrated by the mechanics I have been to. 3 different mechanics with no definite diagnosis.
12-03-2018, 09:39 PM
