I have a 91 explorer sport with 223 k still runing strong just the normal body rot. the way this thing is runing it wouldent surprize me if it lasted to 250K. i was wandring if anybody knows were the altitude sensor is because i know it has one but i cant find it any help would be appectated thanks john

 

I'm no expert, but thought the the 91+ 4.0L had MAF (mass airflow) system which does not require a MAP (manifold absolute pressure) sensor.

Or is this just one more thing that I'm completely stupid about?

 

You're correct, rich. All Explorers use a MAF system. According to the manuals I've read, Ford sometimes put a ambient pressure sensor (equivalent to a MAP, but open to the air instead of to the engine manifold) so the computer would know what ambient barometric pressure is. Those who've found it, say it's on the firewall. but it may not be there at all. I don't think my '92 has one; at least, I've never been able to find it.

 

Hey I found It it is on the firewall and is drectly below the passengers side wiper it has 3 wires and is screwed into the firewall. it is above the evaporator for the ac system on the firewall

 

That sounds like the same place that the MAP is located on my 90 B2.

I thought that the MAF system wouldn't care what the ambient pressure was, since it's measuring mass already (as opposed to calculating mass with the MAP system). Hmmm...

So I guess I'm not completely stupid about this, but I still have much to learn.

Thanks for the info, Mr. Shorty. And glad you found it, jclj.

 

The MAF systems use a BAP sensor (Bariometric Absolute Pressure) which is just an altitude sensing device. Above a certain altitude threshold (~4500 feet) it closes, and the signal elicits a new program from the EEC to compensate for the thinner air. Found along the firewall, sometimes in a plastic pocket.

 

Just a question if anyone is still on this thread, why do you want to know where it is? Are you trying to fix a code/problem or doing something else.

 

ANCIENT post. I'm going to see if my Ranger has one tommorow, just for kicks.

RP
Zach

 

not that I know, as I have said I am not really an electricfied motor guy, on another site someone said that all ford maf based motors have one. Shrug I just don't no why anyone would want to know about it. If its messed with the only thing I can think that it would due is lean out mixture due to less air density and that will pobably lead to piston holes, or at least scorched plugs

 

Some (not all) of the early Ford MAF systems used a seperate BARO sensor which gave a constant feedback signal to the PCM. By the mid-late '90s the BARO sensor was dumped; now the PCM "infers" barometric pressure using other data.

FWIW, my '94 SHO w/MAF has a seperate BARO sensor, mounted on the firewall.

 

Nod so current models don't, but I still don't know why anyone would want to mess with it. however (yes guys I know messing with the computer is bad, but I have more so its kinda fun) if a potentiometer was in line with it and a stoichmeter in the pipe one could control the lean on the system with a lot of restrictions I am sure. But in theory a pot on the ait,and pot on the bar sensor, one could control fuel mixture. I wonder if it would just be easier to control/mix the O2 sensor instead.