A MAP sensor measures the Manifold Absolute Pressure (hence MAP) and is a means of determining an engine's load condition.
A high vacuum is a low manifold absolute pressure. The two are inversely related, so under high load, you have a low vacuum and high manifold absolute pressure. It is normally found after an engine's throttle body, just before or on the intake manifold. I don't know where it's specifically located on the 7.3L.
__________________
Bumper sticker of the year:
"If you can read this, thank a teacher....and since it's in English, thank a soldier
It is located on the passenger side of the firewall, on the heater case. There is a vacuum line on the turbo y-pipe, follow this line towards the heater case and it ends at the MAP sensor.
Originally posted by gburkett Thanks guys, I appreciate the reply. How much does it have to do with the fuel milage?
The short answer is "lots". MAP output is fed into the PCM which controls the fuel injectors. False readings can lead to either lean or overly rich conditions.
__________________
Bumper sticker of the year:
"If you can read this, thank a teacher....and since it's in English, thank a soldier
A couple of diesel specific points that I think are applicable to this thread.
1. There is no throttle body.
2. There is no vaccuum, only pressure.
3. Diesels always run lean.
On the PSD the MAP sensors basic function is to measure the engine load via the amount of boost being produced and send that info to the PCM so that it can adjust the fuel curve accordingly. It's possible that a "slightly bad" MAP sensor could affect the milage, but I would think there would be other, more severe symptoms associated with it. Bad idle, poor running, lack of power, check engine light....that sort of thing.
__________________
Scott - FTE moderator
His: 01 F-250 Lariat, 7.3, ZF-6, NV271. A few mods
Hers: 06 Freestar SEL 4.2l
Would an air leak in the line also cause the milage to go down? meybe I'm crazy or just don't know what it's suppose to sound like but the engine sounds like it's getting air in the line to the injectors. is there a way to tell if you have an air leak in the fuel lines? I appreciate the help from everyone, makes this forum great!
Originally posted by gburkett Would an air leak in the line also cause the milage to go down? meybe I'm crazy or just don't know what it's suppose to sound like but the engine sounds like it's getting air in the line to the injectors. is there a way to tell if you have an air leak in the fuel lines? I appreciate the help from everyone, makes this forum great!
If your getting air in the line to the injectors, you'd be able to tell cause your exaust would be white and smokey. If it sounds like an air leak just after a cold startup and goes away, that is normal.
__________________
2001 F250SD PSD CC 2x4
K&N More to come
Cookie, I have a 01 crew, 4x4. I have done the fuel tank mods and put the inline filter on and changed the clamps like the mod says to. When I bought the truck I was getting about 16mpg. Now I can't get better than 13.5mpg. I have the stinger w/chip and a 203 thermostat so I thought I would be getting better than this! The sounds isn't a hiss or anything.....just sounds like it's missing at low speeds. to me it sounds like it would if there was air in the line but I have no smoke out the exhaust either. I did talk to the dealer once and was told that this was normal milage but I have seen to many others to know that this isn't true. Oh, by the way, I do drive conservately (most of the time).
Is it still cold in Idaho? Might just be winter fuel. Mine got low 15's for the last couple months, but with the return of summer fuel down south it's back to the mid 17's the last 2+ tanks.
__________________
Scott - FTE moderator
His: 01 F-250 Lariat, 7.3, ZF-6, NV271. A few mods
Hers: 06 Freestar SEL 4.2l
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.
