MAP sensor plug but no sensor

[Mr.Crinkle]

anyone know why In 1991 the 3.0L used both MAF & Barometer or MAP sensor and why the 4.0L only used the MAF but still had the plug for a MAP? Does the 4.0 ECU include the input for the sensor? Or does it calculate the atmospheric pressure some other Way

 

[Shran]

Just guessing here but I imagine it had to do with the optional 2.9 engine in 1991 which would have had a MAP sensor, certain states smog rules, and using wiring harnesses for multiple applications... for example, certain years had plugs under the dash for a clutch pedal switch even though the truck had an automatic from the factory.

I have never had a 3.0 truck of that vintage, so I can't speak exactly to that but I haven't seen a 4.0 powered truck yet that had a MAP sensor plug. The early 90's trucks had small design changes here and there almost every single year so really, anything is possible.

 

[Mr.Crinkle]

Smog rules? hmm the 3.0 used an EGR valve and the 4.0 doesn’t, or at lease the one I’m workin on. maybe that’s the reason for the sensor on the 3.0. I guess the plug on the 4.0 is pretty much useless and wouldn’t do a damn bit of good to have it connected to anything if that were the case. Yea that would make sense on the application thing you mentioned. Thanks for reply.

 

[RonD]

MAP or baro sensors were used for estimating air weight, i.e. at sea level or 3,000ft the weight of the air is different

Air:fuel ratios are weight ratios, gasoline uses 14.7:1
14.7 pounds of air for 1 pound of gasoline
14.7grams of air to 1 gram of gasoline

So the weight of the air is very important

MAF sensor does better with "on-the-fly" measuring the weight of the incoming air
So MAF sensor data, Air temp sensor data, RPM and throttle position data can be used to calculate barometric pressure

But when Ford started switching over to MAF sensors they did keep a Baro sensor on stand by just in case all the engineers were wrong, lol

 

[Mr.Crinkle]

Dammit there goes all the horses I was gonna magically gain from a simple sensor

 

[RonD]

You can get lots of extra HP from just one sensor

Say a 2018 F-150
Just pull out the MAF sensor(and the 5.0l coyote engine with it) and install it in the Ranger, a quick 395HP

 

[Mr.Crinkle]

Heh Really. Shows how much confidence they had in their design. You could tell they had more faith in the 4.0 by removing the sensor but still leaving the plug

 

[Mr.Crinkle]

There is no replacement for displacement?

 

[Mr.Crinkle]

I don’t know this all sounds like black magic to me

 

[Mr.Crinkle]

If ford had just stuck with their guns there would have been nothing but 5.0s in all these rangers

 

[Mr.Crinkle]

Besides I thought MAPs were the to go for on the fly response after the hell of reprogramming of course