what is a MAP sensor?

[cruisergt]

Dealer replaced map sensor and PCM after waiting a little over a week for the parts. Car now riding fine. Still wonder if they would have paid for it if I had the stage 1 installed.

[crazyjoe]

they would not have paid for a replacement of the stage 1 PCM, but may have replaced the MAP sensor for you under warranty if it was faulty. I don't think Stage 1 would have done anything bad to the map sensor.

[Big Al]

quote:Originally posted by IRPT

------------------------
From PTDIY:
The MAP serves as a PCM input, using a silicon based sensing unit, to provide data on the manifold vacuum that draws the air/fuel mixture into the combustion chamber. The PCM requires this information to determine injector pulse width and spark advance. When MAP equals Barometric pressure, the pulse width will be at maximum.

The MAP sensor input is the number one contributor to pulse width. The most important function of the MAP sensor is to determine barometric pressure.

Read full article here:http://www.ptdoityourself.net/ptmapsensorguide.html
------------------------
Barometric pressure = outside atmosphere

The sensor does NOT read manifold vacuum. It reads manifold absolute pressure. Vacuum is again a relational representation.

Using the absolute pressure, engine RPM, and a predetermined volumtric efficiency table - the engine controller is able to accurately estimate the amount of air-mass the engine is ingesting.

This of course is used to manipulate the about of fuel metered. The engine load (volumetric efficiency) is also used for spark control and other attributes.

The controller can accurately meter fuel not knowing the barometric pressure. However this added info can help fine-tune the control.

So what happens when this sensor fails and the TIP sensor cannot be used instead? Hopefully the engine controller infers the volumetric efficiency based on RPM and throttle position. However this is not nearly as accurate for a dynamic engine situation.

Pulse width is proportional to pressure. The higher the MAP, the greater the pulse width. In a turbo engine such as ours, this is often much higher than atmospheric pressure - especially at altitude.

[MX-5]

quote:Originally posted by Big AlSo what happens when this sensor fails and the TIP sensor cannot be used instead? Hopefully the engine controller infers the volumetric efficiency based on RPM and throttle position.

Try it.
Unplug the MAP and the engine will die.
Keeping a $23 spare in the glove box could prove beneficial.
In the old days, we always kept a spare ballast resistor, but times have changed.

I replace a lot of Mopar MAP sensors. Each manufacturer has their achillies heel. Mopar MAPs, Ford ISCs & MAFs, and GM coilpacks.

[crazyjoe]

quote:Originally posted by MX-5

Try it.
Unplug the MAP and the engine will die.
Keeping a $23 spare in the glove box could prove beneficial.
In the old days, we always kept a spare ballast resistor, but times have changed.

I replace a lot of Mopar MAP sensors. Each manufacturer has their achillies heel. Mopar MAPs, Ford ISCs & MAFs, and GM coilpacks.

Um, I broke my MAP sensor when I changed my spark plugs the first time. The engine didn't die, and I was able to drive it to the dealer to ask about a new one. Not running at peak efficiency, but still driveable.

[MX-5]

The turbo may have a different PCM strategy for the MAP.

The n/a PT will die.