OK,

Been scouring the forums in attempting to figure out what is wrong. Background... I inherited a M/T 90' RX7 NA S5 from my dad - stock. Original owner, 100K miles. Car has been running however, I noticed that the tranny tunnel was getting super hot. Installed a heat shield, switched out tranny fluid, removed cat (more or less a straight pipe now). After that, I realized it still was running a bit hot - and after looking the FSM, realized that the idle was way too high... staying at 3K RPMS.

So, that started me down the path I am currently down. After fiddling with the idle screw and resetting it via the grounding vis the FSM, no change. I then 'tinkered' with the TPS and adjusted while having a DMM attached... no luck.
I think took it to a Mazda dealership for diags... They came back (and with no surprise) said that they can't fix it. However, the manually forced it and got it idling at 700 RMS... Said it sounded great. What they did say was "May need thermowax, bypass aid control valve, and/or throttle body - All parts unavailable thru Mazda".

So, I then took off the throttle body and:

1. Tested the Water Thermo Valve- seems to be fine
2. Fast Idle Operation - Looked to be out of whack and adjusted
3. Thermal Wax - appears to be working... although, when I removed the water thrermovalve throttle body, the gasket has buildup and looked to be shot. So I replaced.
4. Tested BAC and AWS for both resistance as well as applying 12 V and seeing that they work. All good.

I also figured at this point, I would also replace the vacuum lines (thinking that might be part of the issue). I have replaced majority of the lines. The only ones I have not replaced are the ones that run directly below the extern manifold (didn't want to have to replace the gasket... might need to).

So, at this point, things are better but not resolved. Sometimes, the high idle disappears. After a the engine warms, the idle drops and then oscillates from 1.2K-1.7K RPMS AND the check engine light remains lit UNTIL I depress the accelerator pedal. Other times, the high idle is still there, however, if push in the accelerator pedal slightly and hold, the high idle drops, and the above symptoms persist. I posted a video of this.

I also posted pics of the vacuum line replacement by the solenoids. Reason being is that the routing from the FSM didn't match what I replaced line by line. The FSM shows a line from the Blue relief valve to the bottom of the Gray switch. On my RX7, that goes back to the manifold and attaches to a metal line behind the purge control valve.

Should I get the external manifold gasket and replace the rest of the vacuum lines? I did use brake cleaner and sprayed around the air pump and all connections of the vacuum lines while the car was running without success. I am stumped on what to do next.

 

Welcome to the forum. First thing to do would be to pull the codes and see what you are getting. Factory Service Manual can be found at Foxed.ca, or Rotaryheads.com. Second thing I would check would be that your vacuum routing is correct, and check for vacuum leaks by sealing the system inlet and using about 5-10psi of compressed air.

 

Can you elaborate a bit more on pulling the codes.... I have a DMM, but I don't have the Mazda Service Code machine.. nor do I know where to get one. I could take back to the dealership, but I don't think they are really of much help since the check engine light was not on before I took it to them. And, since this is a project car, it's been a month or more since they had it.

As for the vacuum routing... I did use the FSM and followed the diagrams. I actually just replaced 1 line at a time and marked it off the diagram. However, as I posted above, the output of the relief solenoid valve (Blue) in the diagram goes below the Switch Solenoid Valve (Gray).. but in my car, it went to a nipple on the other side of the PCV (Picts show a little bit of blue there) (and the check valve is still there).

And for the leak... you say to seal the system inlet? I saw someone else had used a PVC cap on the input to the air pump and used compressed air... And what about the lines I didn't replace under the external manifold.. could I still hear air leaking from them? or would it be best to rent a fogger and fog the system via the input to the air pump?

 

I would spray starting fluid around the intake, vacuum lines, etc. and see if the idle jumps up. It's a long shot, but it could be you injector grommets.

 

There's a green (I think) single wire connector near the battery, ground it to the negative terminal and the check engine light should start flashing codes. Google what the codes are and how to read them. Basically it flashes the number at you with long and short blinks and that tells you your code.