MAP/BAP sensor help..

[Mavrick]

Whichever it is on a MASS AIR car. Mine has no vac hooked up to it, just atmospheric pressure. I think its the MAP sensor?

Either way.. my car has a slight miss. I can feel the motor jerk every 3-5seconds and i can also hear/feel bursts of air or popping out the drivers side tailpipe. A buddy told me it could be the MAP sensor.. so i unplugged it while the motor was running. This threw a CE light but did not change how rough/smooth the motor ran.

How can i test the MAP sensor to know for sure, whether or not i should replace it?

Thanks.

 

[jrichker]

Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

Code 22 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture and changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

 

[Mavrick]

It is not throwing a code. When i unplug it while the car is running, it makes no change in how the motor runs. Is this a problem? I tried this because a friend told me that it may be the culprit to my motor having a miss.

 

[Euphoric306]

dont unplug the mass air sensor when the motor's running.... just dont

and if ur computer's not throwing a code at u after u did that... maybe thats ur problem

sounds more like an ignition problem to me... check ur rotor and dist cap... check cap for wear on terminals and cracks... even unseen ones can collect water and send spark to the wrong cylinder

are your wires in good condition?
check reisitance in coil, if i recall i should be less than .5 ohms or something

doesnt sound like a sensor problem to me, but its at ur house and not mine

 

[ratrapp2]

if your car is mass air and doesn't have vacuum running to it then it's a bap sensor.non-mass air cars use a map sensor.it's the same sensor just not hooked to vacuum.

 

[stang22]

if your car is mass air and doesn't have vacuum running to it then it's a bap sensor.non-mass air cars use a map sensor.it's the same sensor just not hooked to vacuum.

Tim

 

[Mavrick]

dont unplug the mass air sensor when the motor's running.... just dont

and if ur computer's not throwing a code at u after u did that... maybe thats ur problem

sounds more like an ignition problem to me... check ur rotor and dist cap... check cap for wear on terminals and cracks... even unseen ones can collect water and send spark to the wrong cylinder

are your wires in good condition?
check reisitance in coil, if i recall i should be less than .5 ohms or something

doesnt sound like a sensor problem to me, but its at ur house and not mine

Sorry for the confusion.. it was my BAP sensor that i tried unplugging while the car is running.. and yes, as soon as i unplugged it, the check engine light came on. I meant to say that, it is not throwing a code when it is hookedup.

My wires are FMS blue wires.. previous owner bought them "used" - Maybe i'll look into replacing them.

Any other suggestions for my slight miss/stumble?

Thanks,