JeffRX7

my 87 n/a is having a weird problem mostly to do with the idle... On a cold start, the car starts up fine and rests at a nice high idle like it should, once it warms up though, the idle drops to like 600, surging lower, constantly wanting to kill. I've backed the idle screw out as far as it can without lifting off the rubber seal, and i leaned it out a little which brought it up a hare, but still, same result. when trying to troubleshoot it, i disconnected the vaccum line going to the pressure sensor from the manifold. the car then would have a high idle, 1200rpm, but idled great and smooth, and seemed smooth all the way to redline. I took it for a hot lap and it felt better than ever from 5500 up but i felt a loss in the lower range. It continues to run great that way until that vaccum outlet is covered or the sensor is reconnected, then it just dies. Anyone have any ideas on this? normally i would think a vaccum leak would cause symptoms like this, but instead one is helping... oh, some other info bout my car, i did remove the airpump, ac/cv, have full exhaust and K&N cone intake, and have a #9.5 flywheel. I'm about to start a turbo conversion on the motor, and I want to make sure everything is functioning correctly first, hoping that nothing mechanically is wrong but it seems more like a (fuel,ignition,or air) problem to me... any help would be great. also if anyone has any tips on putting a turbo on an N/A that would be great too.

mazdamanda

Maybe your pressure sensor is bad? There's a way to test it, but I'm not sure how. Try searching. As for turbocharging your N/A there are different ways of doing it. Check out these websites:
http://www.aaroncake.net/RX-7/naturbo.htm
www.rotaryresurrection.com (tech section)
I personally recommend doing the full conversion.

silverrotor

iTrader: (1)

I'd check the Pressure Sensor. Do not leave It disconnected! The ECU Is dependant on this for many functions. Bump the Idle up and see what happens.

JeffRX7

What all functions of the ECU does the pressure sensor effect? I drove it the rest of the day today with it unhooked and the car has run better than it has in a while. As far as the pressure sensor being bad, even if it was bad, it wouldnt be relieveing any pressure as unplugging the hose does. it just is a diaprahm sensor for pressure as i understand it. Is there any way to adjust the idle other than the set screw on the top of the throttle body? that one is adjusted to the max. I could adjust the throttle cable some, but every time i try doin that it throws the TPS off and out of adjustment range. anyone?

JeffRX7

also, I was under the impression that the pressure sensor on a n/a car was there to sense manifold vaccum pressure, but when the hose is disconnected, the fitting on the manifold blows air out. Is there supposed to be positive pressure in the manifold? I thought it would only be vaccum, and that you'd get positive pressure from boost, which i don't have yet... help?