Barometric pressure sensor?
- Thread starter 88 Fox GT
- Start date
Rootus
Officially Addicted
mo_dingo
20+ Year Stangneter 
stang_gt_1994
Founding Member
95strokerPSU
Member
94-95 don't have a BAP sensor. I did the PIH switch and in the process pulled up a wiring diagram from All Data to compare the 93 to a 95 computer. On the 93, pin 47 goes to the BAP and on the 95 it goes to the Mass Air. So I would conclude that 94-95's are controlled through the mass air.
95strokerPSU
Member
Silver85TC said:
What do you want to know about it? If you want to know what pins control function (i.e: Pin 47 controls Mass Air), I have print outs from All Data that show a 1993 5.0 wiring diagram and also 1995 5.0 wiring diagram. If that's what you want I could maybe fax them to you.
I'm trying to eliminate a very minor random tremor at idle. It shows up as the RPM's drop below 1000. Most people don't notice it until I point it out to them. The idle RPM doesn't change at all on the tach (700 RPM), but it's just enough to cause the engine to shake a slight amount. (I know, I'm being very anal!) It's almost like I've got a bit of a cam in the car.
The minor stumble is a little more obvious when the car is cold, and almost disappears when the car is warm. The car runs as smooth as silk above 1000 RPM and pulls very hard all the way up to redline.
I've done a complete tuneup, checked codes, cleaned MAF sensor, EGR valve and IAB valve, new IAT/ECT/O2 sensors, new balancer, new motormounts and haven't been able to find any vacuum leaks. Except for a 190 lph fuel pump and a cat back, my car is pretty much stock.
Anyways, that's why I was asking about the BAP sensor and the differences between the 94/95 PCM and the Fox PCM. I've heard a bad BAP sensor can cause minor problems, but that's obviously not it since our car's don't have one.
I've also heard that this was a very common problem with the 94/95 GT's and Ford even issued a service bulletin stating that minor motor shake at idle was "acceptable"?!?! WTF?
I've owned 3 other Fox 5.0 Mustangs, and they all had an extremely smooth idle.
Anyone have any more information or ideas on this?
Just ignore this post if you think I'm being to anal!!!
The minor stumble is a little more obvious when the car is cold, and almost disappears when the car is warm. The car runs as smooth as silk above 1000 RPM and pulls very hard all the way up to redline.
I've done a complete tuneup, checked codes, cleaned MAF sensor, EGR valve and IAB valve, new IAT/ECT/O2 sensors, new balancer, new motormounts and haven't been able to find any vacuum leaks. Except for a 190 lph fuel pump and a cat back, my car is pretty much stock.
Anyways, that's why I was asking about the BAP sensor and the differences between the 94/95 PCM and the Fox PCM. I've heard a bad BAP sensor can cause minor problems, but that's obviously not it since our car's don't have one.
I've also heard that this was a very common problem with the 94/95 GT's and Ford even issued a service bulletin stating that minor motor shake at idle was "acceptable"?!?! WTF?
I've owned 3 other Fox 5.0 Mustangs, and they all had an extremely smooth idle.
Anyone have any more information or ideas on this?
Just ignore this post if you think I'm being to anal!!!
MLC Stang
Founding Member
Guys,
A BAP (Barometric Absolute Pressure) sensor is required on cars that use the old Speed Density method of determining engine load. This is an idirect method involing calculations from various sensor readings including the BAP.
Our cars use the MAF (Mass Air Flow) sensor to directly measure engine load by determining the mass of the incoming air charge. No calculations or BAP needed. The MAF does it all.
My old '88 Lincoln Mark VII LSC had one on it because it used Speed Density, not a MAF.
A BAP (Barometric Absolute Pressure) sensor is required on cars that use the old Speed Density method of determining engine load. This is an idirect method involing calculations from various sensor readings including the BAP.
Our cars use the MAF (Mass Air Flow) sensor to directly measure engine load by determining the mass of the incoming air charge. No calculations or BAP needed. The MAF does it all.
My old '88 Lincoln Mark VII LSC had one on it because it used Speed Density, not a MAF.
donjohn
New Member
That's not quite correct. All of the MAF Fox Mustang's used a BAP sensor. The speed density 5.0's used a MAP (Manifold Absolute Pressure) sensor. The sensor itself looks the same for MAF and speed density. The only difference was the MAP sensor was connected by a vacuum line to the intake manifold and the BAP sensor was open to the atmosphere.
94/95 was the first year where a standalone BAP sensor was not used on a MAF 5.0 mustang.
That would be why the 94/95 5.0 Mustang is so sensitive to MAF meter problems, compared to an earlier Fox 5.0 Mustang.
Hope that clears things up.
Cheers
I stand corrected!
I've been talking with a guy at The Corral who says there is an actual BAP sensor located inside the case of the PCM on 94/95's. The MAF meter is not used in this calcualtion. I'll post more when I find out where he gets his info from.
I must admit I'm becoming very confused now!
Cheers
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