Can somebody tell me how a Mass-Air-Flow meter works?
My '96 302 F150 needs a little help with high revs and burning rich (according to codes) All seem to point to MAF sensor, which I've checked and cleaned. Trying to avoid buying high dollar sensors if it can be avoided. Need an education from one of you smart people.
Without getting to technical a MAF has 2 wires inside one of them is heated and as the air passes over it the element is cooled and changes voltage.The computer uses this info to make a calaculation on the amount of air comming into the eng to determin fuel deleviry,It also uses this info and other info to calaculate barometric pressure to compensate for elevation.What we find is that the heated element get contaminated and throws of the baro calculation witch will throw off fuel delivery.silicon is the biggest contaminate for this sensor and is very dificult to clean off.If you have scan tool you can get a baro reading to check to see if this is your problem.I dont know were you are in relation to sea level but at sea level the baro should read 157 Hrz.As elevation increases you baro will go down in frequincy.Exaple at 8000 feet above sea level you baro would be about 140 Hrz.If I can be any help you may email me.
as for the guy who thinks the baro and maf are 2 different components I would like him to tell me where the baro is on a 96 bronco I would be very interested to hear that.
There may not be one. It would most likely be mounted in the same position as the MAP sensor in older speed density trucks if it uses one. The MAP sensors are mounted to the passenger side firewall just below the cowl if it's indeed in the same place. The MAF signal does change slightly with respect to ambient air density and temperature, but it does not make a direct measurement of barometric pressure (this is fact, not something I "think"). Some newer MAF meters have air temperature sensors built into the unit, but not all MAF meters do.
A 2 wire MAF has the BARO sensor built in, just like on my 01 F150 5.4L.
A single wire MAF like on my 88 Mustang has a separate BARO sensor on the firewall which used to be a MAP sensor with speed density.
On the 96 truck in question, there is no barometric pressure sensing capability within the MAF meter itself. What do you mean by single or two-wire MAF? They have always been four or six wire in the Fords I've seen.
To try and straighten this out correct that there is no phisical baro on this truck the pcm uses info from a few different sensors to make a calulation of a barometeric pressure.The MAF is the main input to this calulationI see the web site has tsbs andrecall info if you check there is a tsb that has use here at fore checking what is called the baro pid to see if it correct for the elevation we are at us being at the shore I am at sea level but if the baro read below 157Hrz.usual we see a reading of 139Hrz when we engine runig problem but at that point that the baro reading is wrong the next step is to replace the MAF and reset the KAM this is fact and you can look this up because it is a tsb and is used accross the ford,linc,merc line.In speed desity engs your correct that the baro is part of the MAP,and yes some of the newer model use a baro sensor on the firewall that is a MAP sensor with no connection to the eng.If you refer to tsb 98-23-10 you will see what I am tryin to explain here on the issue of MAF affecting the baro reading in the pcm.
I'll add that OBD1 trucks used seperate firewall mounted Baro/MAP sensors for both the SD and MAF versions. I won't comment on OBD2 vehicles as they may have been different, and this '96 should be an OBD2 vehicle. In both cases, the computer will give specific codes for the MAF sensor if it detects a problem with it's input, a code that states the mass air meter outputs are outside the recommended range is very likely a MAF meter problem, though it could be a contaminated or failing sensor or faulty wiring.
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Paul O
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1990 F150 4x4 XLT Extended Cab (Currently undergoing a heart transplant)
1990 Ranger 2wd, 2.3 Briggs & Stratten, 5-speed, 3.08
If you refer to tsb 98-23-10 you will see what I am tryin to explain here on the issue of MAF affecting the baro reading in the pcm.
The baro reading referred to in that TSB is inferred from the sensed flow characteristics sent to the computer from the MAF. Yes, a dirty MAF sensor can cause an incorrect barometric pressure reference to get stored in the computer's memory. However, there is no barometric pressure sensor contained within the MAF sensor itself for any of the vehicles covered by that TSB (1990-1999 mostly, which includes this 96 Bronco). I do see where you're coming from since baro trouble codes on newer vehicles can be related to the MAF.
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