I had a hell of a time trying to get my engine to run properly after an engine transplant. I got a lot of help from this forum (for which I am very grateful) and I am almost there now. The OBD I bought helped my identify that my ambient pressure sensor was reading low ( I expected amibient to be 30" Mercury). when I pulled the vacuum line to the sensor, the reading became 30" and the engine ran much much sweeter- no more kangarooing. My question is, what should the sensor be connected to? i traced the hose that was making life hell for me and it was connected to the side of the inlet manifold. If I resore this connection, the car runs like crap again. My other question is, where should the vacuum line on the side of the inlet manifold go if it should not be connected to the ambient pressure sensor?

Thanks

 

The ambient pressure sensor should be open to atmosphere.
Look at the shop manual.

 

sounds like the one that would normally go to the vfad .....

 

You have connected a hose to the barometric sensor? just ahead of the air pump?

It needs to be open to the atmosphere, and that hose/nipple can be capped if you don't have a VFAD system.

S

 

ok guys what is a VFAD system?
also, why does the baro sensor have a connection for a vacuum hose if nothing needs to be connected to it? I have looked in the manual and my manual has nothing on the barometric sensor. Thanks for your input.

 

Its not a vacuum hose. Its just open to atmosphere.
Page 312 of the engine details section of the shop manual.

 

VFAD is the stock system in the airbox that lowers intake noise at low rpm's by sending the air through a resonation chamber. The VFAD is electrically controlled and vacuum operated to open up at 4,250rpm? and provide a straighter path of air to the airfilter. If your stock intake has been changed to Mazdaspeed, or aftermarket, (or a prior owner just liked the 'whoosh'), the VFAD plumbing is either bypassed or no longer under the bumper - hence capping the vacuum line that controlled the damper.

 

since it's mounted on the chassis rather than the engine I'd be suspect about the actual issue since it likely wasn't related to the engine transplant

further, it's just a sensor with a 2" long piece of tube open to the atmosphere so I'd be even more suspect that you have the wrong device pegged in the first place the same as everyone else

sounds like you don't have a shop manual, bad idea ...

 

We all know what we think you are talking about, but how's about a nice pic to show us to make sure!

 

many thanks for the guidance. Page 312 said it all. I never went that far into the manual before!!!
I now also know that I have a VFAD system and that it is connected properly.
I looked at the inlet manifold and saw that there were two tapping points. one that was capped using a rubber bung and the other had been connected to the ambient pressure sensor. I removed the hose and capped the inlet manifold end, the left the ambient pressure sensor open to atmosphere. the car runs wonderfully now.
thanks team!!