atlas541

ok, i need to know where the vac line from the atmospheric pressure sensor on my '87 NA is supposed to plug-in on the engine. i had to replace MANY hoses and i think i may have lost where this particular one goes. ive been digging through my 88 shop manual, but the vac line routing diagram shows the hose just dropping somewhere behind the picture next to the intake.


also, as far as testing the APS, it says to connect a voltmeter to the plug, terminal D, but does that mean i unplug it and connect from the plug-side? or does it mean i need to stick a probe into it from the wire-side of the plug
?

thanks everyone
Mike

atlas541

ok nevermind, i realized later that night that the pressure sensor is supposed to be open to ambient air (duuuh).. but anyway, that leaves me with a new problem.

When I have the single vac nipple (on the middle part of the intake) plugged, and the pressure sensor open to air, my o2 sensor never goes into closed-loop while im driving. Now, with the pressure sensor plugged into the vac line on the intake, the o2 sensor runs closed-loop while im driving nice, just like its supposed to.
Also, the car seems to run fine however this little arrangement is hooked up.

I can monitor closed-loop status on the o2 sensor by means of the LED diagnostic wire setup as described elsewhere here in the forum.

So anyway yea this totally boggles me, because I would like to have my vac lines hooked up correctly and still be able to run my o2 sensor in closed-loop.

btw my car runs an 88 N/A with mostly removed/plugged emissions.

stevej88na

You solved your own problem, almost. The pressure sensor plugs into that vacuum port, it senses manifold pressure. The atmospheric pressure sensor near the ECU senses atmospheric pressure. To make sure we're talking about the same vacuum port, check out the photos here:
http://howto.globalvicinity.com/gv_w...i=44&co=1&vi=1

I just realized it's hard to tell where the pressure sensor's going there, I'll have to take another photo.

atlas541

so the black box with the 4-wire plug and the 1 vac nipple is the pressure sensor and NOT the atmospheric pressure sensor? im having trouble identifying where my APS is, which is frustrating because the car seems to work fine but the ECU throws code 14 all the time, even with a reset.

also, what is this "pill" for that's mentioned as part of the pressure sensor hose? i just have a direct hose, no T's or pills or anything. Do i need it?

again, thx

stevej88na

That's the pressure sensor you're talking about, it's near the passenger-side suspension tower. The APS is near the passenger's feet inside the car next to the ECU. The pill is shoved somewhere in that single vacuum line to filter out sudden manifold pressure changes - you should make sure you still have it.

atlas541

ahhh ok.. so, what does the APS look like then? I ask because I put this engine in my '83 a couple years ago, so there are random wires all over, not to mention a few parts prolly missing (like the APS), since I had to find a junkyard ECU and complete wiring harness, and find a creative place to fit it under the hood of my '83.. i guess it doesnt really matter anyway right since with no APS the ecu defaults to sea level?

oh, yea i dont have the little pill for the pressure sensor, its long gone..

HAILERS

The atmospheric pressure sensor (ATP) looks similar to the pressure sensor in the engine bay. Except it has NO vacuum nipple on it.

The part number for the ORIFICE can be found on this site using the Search engine and putting in ORIFICE and HAILERS. Or go to the Mazda dealer and buy one. Or make one. Or do without one. OR download the parts fische and look for the part number. Or??

atlas541

lol

awsome, thanks

i guess unless i really need one ill just do without the orifice..
now i just need to find an atmospheric pressure sensor in a junk yard..

stevej88na

HAILERS buttons up another thread!


PS: If you end up waiting a while, I'll be done with my AFM to MAF swap, and you can forget the ATP all together.

My5ABaby

iTrader: (7)

You need to finish that up.

stevej88na

It's definitely high on my list. I'm finishing the display/logger first though!

My5ABaby

iTrader: (7)

Ugh, that one looks complicated.

Hopefully the MAF one will be simpler than that electronics-wise. Either way though...

HAILERS

I read that link and have a suggestion. This being the RX-7 Owners Club, you might want to keep the cost of the chips down. Two fifty apiece is pretty rich for this forum. (humor)

stevej88na

Ha! No comment.

stevej88na

Thanks! Yup, the AFM circuit is way less complex than this one. There are basically two chips for the AFM swap, and seven for the display so far.

PS: HAILERS, I hear you never check PMs - that true?

HAILERS

PS: HAILERS, I hear you never check PMs - that true?

Never ever unless I'm selling something.

And...........from the RTEK2 (Pocketlogger). experience where they use a Palm to view and make adjustments to the ECU, I guarantee you if you build something and put it up for sale using your current viewing option, they will want you to have a serial port on it so they can log and view it on a DAMN laptop. (humor but sadly true. Idiots.).

HAILERS

By the way, if you want to make some pocket change and a name for yourself, someday you might make a digital compression tester using a DATAQ unit and a pressure sensor plus a hose to the sparkplugs.

It's been done on this forum (first gen area not second) but never put into a package that someone could buy. Then again you'd never make much money what with folk who use toilet plumbing for TID's.

stevej88na

It already has a serial port for getting data dumps after the fact, but not for real-time viewing. Unlike the Rtek, this won't tune anything, it only logs. I also don't plan to sell these, but I'll put the code and design up for others to try on their own, like I did with the solenoid VDI actuation project.

stevej88na

That does sound interesting, but if I did it, I'd put it up open source like all my other projects. It looks like pressure sensors that would do the job run about $100:
http://www.digikey.com/scripts/DkSea...588274&Site=US

From there, I'd use chunks of the LCD project code to log and upload via serial to a computer for display. The memory would have to be changed though, because it can't handle 1kHz writes. Another option is to display the three compression values on the LCD and not worry about logging and memory at all. That might be best, and would only need one pressure sensor, one microcontroller, and the LCD.