96 f250 engine code (172)
Thread Starter
|
New User
Joined: Oct 2009
Posts: 10
Likes: 0
96 f250 engine code (172)
I had a friend pull the codes on my girlfriend's truck (96 F-250HD, 351, auto, 4x4). The code he pulled was 172 which says the truck is running lean on the right side. My question is, is this an oxygen sensor or something else causing it to run lean. What are the common things to throw this code? The truck also has a whining/whistling noise. It sounds like a vaccum leak, but i can not find any. I have checked all the hoses under the hood. Any help would be appreciated.
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,751
From: Kentucky
The 172 code indicates the O2 sensor is sensing a lean condition. This is usually caused by a vacuum or exhaust leak. You really need to find the cause of the whistling noise. Check the air pump fittings and lines. How did you check the underhood hoses? A visual check or spraying with carb. cleaner is not a 100% accurate method.
On these fuel injected engines I have found using a hand held vacuum pump/gauge to test each line, circuit, component is the only way to verify 100% if these items are in top operating condition without resorting to finding a shop that can perform a "smoke test".
The exhaust is another problem area for the home mechanic to diagnose and repair. Most common areas for leaks are the manifolds themselves, the ball and socket connection to the y-pipe and the air tube leading to the converter. Anything down stream from there typically has a smaller affect on the O2 sensor.
On these fuel injected engines I have found using a hand held vacuum pump/gauge to test each line, circuit, component is the only way to verify 100% if these items are in top operating condition without resorting to finding a shop that can perform a "smoke test".
The exhaust is another problem area for the home mechanic to diagnose and repair. Most common areas for leaks are the manifolds themselves, the ball and socket connection to the y-pipe and the air tube leading to the converter. Anything down stream from there typically has a smaller affect on the O2 sensor.
Thread Starter
|
New User
Joined: Oct 2009
Posts: 10
Likes: 0
To check the hoses, I used a hand held vaccum pump/brake bleeder. I plugged one end of each hose and hooked the pump to the other and held the vaccum for a little to be sure they didnt leak. The hoses that leaked, I replaced/repaired.
As for the exhaust, I replaced the passenger side manifold 3 months ago because the old one cracked. There is no catalytic converter on the truck either.
This kinda leaves me wondering because the truck is getting about 8mpg now.
As for the exhaust, I replaced the passenger side manifold 3 months ago because the old one cracked. There is no catalytic converter on the truck either.
This kinda leaves me wondering because the truck is getting about 8mpg now.
Post Fiend
Joined: Jan 2005
Posts: 8,402
Likes: 10
A good way to check for vacuum leaks is, with the engine at idle, spray carb cleaner around the intake manifold and pipes and listen for a change in engine note.
Might be a good idea to hire a fuel pressure gauge and see what the fuel pressure is.
Might be a good idea to hire a fuel pressure gauge and see what the fuel pressure is.
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,751
From: Kentucky
It sounds like you covered the basics of hoses and exhaust leaks pretty well. I agree with Lazyk about the fuel pressure check next. Then the next suspect item is the O2 sensor itself is just plain lazy... they tend to slow down their swing between rich/lean as they age. But it is never a good idea to blindly throw a new sensor on before checking/repairing all the other items first.
Thread
Thread Starter
Forum
Replies
Last Post
Soarer
1987 - 1996 F150 & Larger F-Series Trucks
3
Aug 18, 2014 05:19 PM
digicon
1987 - 1996 F150 & Larger F-Series Trucks
16
Jun 4, 2014 01:10 PM
93coleman
1987 - 1996 F150 & Larger F-Series Trucks
2
May 31, 2010 03:47 PM
