p0171 and 174
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p0171 and 174
So I have a 1997 ford f150 v8 4.6 2w
I got codes p0171 and 174 my truck seems fine till the idle drops it's weird when I have it on park it's fine if I turn the wheel left the idle drops when the ac turns on the idle drops and it's wasting crazy gas
Where should I start first in finding this problem?
I got codes p0171 and 174 my truck seems fine till the idle drops it's weird when I have it on park it's fine if I turn the wheel left the idle drops when the ac turns on the idle drops and it's wasting crazy gas
Where should I start first in finding this problem?
Lead Driver
Joined: Sep 2006
Posts: 7,907
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A look at the code descriptions will tell you the motor is running lean.
A lean condition is to much air.
The Computer has shifted the fuel tables rich to account for the fault.
This why the idle and gas consumption is out of wack.
Find the air leak into the intake tract.
Look at the PCV hose rubber fitting in the rear of the vertical intake manifold as a start.
Good luck.
A lean condition is to much air.
The Computer has shifted the fuel tables rich to account for the fault.
This why the idle and gas consumption is out of wack.
Find the air leak into the intake tract.
Look at the PCV hose rubber fitting in the rear of the vertical intake manifold as a start.
Good luck.
Tuned
Joined: Apr 2013
Posts: 354
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From: Katy, Republic of Texas
Yup, 171 and 174 means a major vacuum leak since it is both the left and right sides.
Usually a connection (or leak) somewhere on the manifold. Check the intake tubing and as said, the PCV hose elbow on the back of the air intake.
Usually a connection (or leak) somewhere on the manifold. Check the intake tubing and as said, the PCV hose elbow on the back of the air intake.
Fleet Mechanic
Joined: Aug 2008
Posts: 1,446
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From: NE Iowa JD Country
Does the HVAC inside the cab direct the air where you want? or does it just do what ever or is stuck in one position?
How do the brakes feel?? pretty solid or spongy? or do they fade if on the brake peddle for extended period? (long light)
How do the brakes feel?? pretty solid or spongy? or do they fade if on the brake peddle for extended period? (long light)
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I am having the exact same issue with my 5.4. I've read on other places that it could be the upstream o2 sensors are bad.
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Joined: Jan 2004
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From: St Louis
This code pair is almost always caused by either an intake vacuum leak, contaminated or defective MAF sensor, or a weak fuel delivery system that is not delivering adequate fuel volume at pressure. 90+% of the time, it's an air leak and it's almost always the PCV system at fault. Once in a while, it will be a cracked intake manifold or gasket or, on some engines, the isolator bolts.
Spray some carb cleaner around the upper intake manifold and the hoses there. If the idle stumbles you have narrowed the area down to where you are spraying.
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Joined: May 2016
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Ya man the brakes feel spongy and loose
Senior User
Joined: Nov 2015
Posts: 140
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From: Heber, UT
mileage
could be air in brake lines,But in your case... sounds like a good size vacuum leak , check the pre formed elbows on intake area vacuum lines, have had them split right open on the underside of elbow where you cant see them
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