What's meant by "vacuum leak"? Which components is that related to, or how do I test for it?

Thank you.

-C1911

 

its leaking vacuum hose ,cracked,broke,missing,
you will have to check all your vaccum lines unless you can tell us whats not working

 

A vacuum leak is where your engine is sucking in air from where it shouldn't as relating to the inlet manifold.
All the air needs to go through the MAF or carb so that fuel is metered properly.
If you have a leak on any of the gaskets, then you have a vacuum leak. It can also be caused by a hose falling off or leaking, i.e. the hose to the brake booster.
You can check for this by spraying the suspicious area with an inert fluid which will seal briefly.

 

Same P0175 story, mixture too rich. Truck runs great, feels great, 800idle, 2000RPM driving, but 11mpg. F150 XLT 4.6 V8. 2002. So someone said to check for vacuum leaks, so I asked what they were. I checked PCV and it's fine.

 

Which one is the vacuum hose?

 

Ya all missed that code 175 is only bank 2, and not common to the whole system.
A vacuum leak is common to all except at areas right at an intake runner into the head that could cause one cylinder to run differently.

Look for an exhaust leak from the header back to the first ox sensor that is letting air in and causing the sensor to react by richening up that bank in response to the extra air or even an faulty sensor, heater or plugup.

An unsealed exhaust system can draw air in as well as leak exhaust out during the negitive positive pulse time pressures.

An open sensor cable most times will cause the PCM to revert to a rich condition on that bank and set the code.
Takes a bit of effort to find it.

 

I looked under my truck and saw the four items that I'm guessing to be oxygen sensors. They all looked the same and when I looked at one of them up close, it said BOSCH. That's not OE, that's aftermarket. I wonder why would O2 Sensors be replaced on a truck. Why four? On a '02 at 55k miles?

And also, I wonder if the previous owner replaced them in an attempt to fix this same problem I'm having and it didn't fix it, and he just said f- it and sold it..?

Also, BTW, I guess the sensors aren't the problem.
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As to the ACTUAL stuff people mentioned, like vacuum leaks, I checked around the transmission area what I could about visible damage to hoses and found none. I only saw so much though b/c I was laying under a parked truck.

Wonder if I ought to take it to a service shop somewhere.. Really don't wanna be paying 75 dollars for a diagnostic, though.

 

Ford used Bosch O2 sensors from the factory.

 

The problem with the whole vacuum leak theory is that a vacuum leak causes excess AIR in the system which makes it run LEAN, not rich.

P0175 System to Rich (Bank 2) Detailed Description
The Adaptive Fuel Strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a lean calibrated limit.

Possible causes :-
Air Measurement System.
MAF sensor (contaminated, damaged, corroded connector, etc.).
Fuel System.
Fuel pressure regulator (vacuum hose off, diaphram leak, malfunctioning, etc.).
Leaking fuel injectors.
Fuel return line restricted.
Fuel rail pressure sensor (incorrect reading).
EVAP canister purge valve leak (when canister is full).
Base engine.
Engine oil contamination.


Diagnostic Aids
View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s).


The reason for the four sensors is simple. The two upstream sensors monitor the engine's output and help the system adjust the air/fuel mixture for optimum performance. The two downstream sensors monitor the catalyst's output to make sure the catalytic converters are operating properly.

Hope that helps.

-Joe

 

When you say "quick question" do you want us to read it fast,or are you typing it fast! Sorry,I just had to!
Anyway,have you looked at the O2 sensor to see if excess water is dripping on it,causing it to short out and throw the code? My friends 98 E150 van had the same problem and it was from water dripping on the O2 sensor.

 

Another quick and simple thing to try is to swap sensors from one side to the other. If the problem moves, it's the sensor. If the problem stays there, it definately means that side's getting too much fuel from somewhere.

-Joe

 

[Raoul]It's when your shopvac has a hole in it[/Raoul]