Yeah, something's not good with how that secondary rail is fitting. May want to remove it and get us some pics of what you have in there.

Typically that seal goes in the hole then the rail sits on top. You may already have a seal in there or something, they get rock hard over time so it may look like it's just the plastic diffuser.

Dale

 

I did not see any orientation for the injectors diffusers, and didn't see any side for the grommets neither...

Seal is new and far from solid. I tried something else. I installed it exactly like it was before. Still seems strange to me, fuel rail just goes on top of the grommets?

This morning, I bolted everything back (freshly cleaned LIM with renewed RTV on all 3 block-off plates). I did not bolt the turbo to the manifold. Same problem. High idle, if I get it below 1,600 RPM it bounces. RPM still drops when I spray brake cleaner/starting fluid at the LIM to engine block gasket area (front). Could it be because of the high RPM when I do that test (1,600 RPM)?

I've been chasing that high RPM/bouncing idle issue for 2 weeks today.

 

When you have the high RPM is the throttle totally closed or is the primary throttle stop still cracking the throttle open?

Dale

 

I do not understand. By the primary throttle stop, do you mean the screw in front of the TB? If so, yes, it is "cheated" (over specifications).

There is absolutely no way to get the car idling if I respect the VTA1 & VTA2 OEM specifications.

 

Your high idle is coming from that throttle stop screw at this point. If you screw it in so the TPS is where it should be does it start but just not want to hold an idle/stall out?

Dale

 

Yes exactly! If I adjust it to be within VTA1 and VTA2 OEM specs, it starts but cannot idle.

 

Dude I can't wait for you to get this guy running right!! I've been popping in from time to time to check on your progress.

Props for going at it on your own instead of just throwing it at a shop to fix!! That satisfaction you'll feel when it's happily purring along will be well deserved!

 

I would unplug the iacv and go to a manual idle. Sounds like not enough air is getting pass the throttle body to give you an idle. maybe the iacv is the problem.

 

Thank you sir! But to be honest with you, right now I'm thinking of sending the car to a shop more than ever to fix that bouncing idle (car has to go there to get tuned anyway).

Never heard that idea before. How do I do that, I simply unplug the IAC? By the way, I tested the IAC last week by removing it, cleaning it and plugging it directly to a battery.

 

ditto im rooting for ya, and happy to see the help being offered.. awesome community

 

I'm also amazed by the amount of help I got here. I took my engine out and rebuilt it all over by asking questions here at almost every steps of the process (and it seems to be running fine, despite that actual idle issue).

I can't believe that community.

Not every car forums are like that.

 

Takes a LOT of perseverance to do that !

 

Keep going and you'll get there

 

And a lot of patience! I'm glad I've got other sports cars to play with in the meantime. I don't want to get off-topic too much, but I recently met a woman and she told me that "the red car" (RX-7) seems to be the fastest of all my cars (I've also got a Viper, Corvette C4 ZR-1 and a C63 AMG). It kind of gave me a moral boost to work on the RX-7!

Thanks! I feel like I'm almost there. My aftermarket oil pressure sender has been broken forever, as well as aftermarket coolant temperature and wideband. Everything is fixed except for the oil pressure sender which is supposed to arrive in the next few days. Right now I'm trying to get every details fixed, and when it is going to be done I am going to send the car to the tuning shop. Hopefully the bouncing idle will be fixed before, or I'll just ask them to find the problem and fix it. I also received a new set of spark plugs 2 days ago, I will give it to the tuning shop when the time comes.

I already asked it twice here, without any conclusive answer:

My F100 module (CPU #2) is broken, completely dead. I heard from a local guy that the '96+ module is plug and play and never fails. Can someone confirm that information? That local guy is well-known but I'm very skeptical.

 

https://www.rx7club.com/power-fc-for...-setup-870320/

Good read about manual idle

 

I have a 99 FD and had the stock CPU 2 do exactly what yours was doing until I replaced it with a used one, which completely resolved the problem. Just weighing in on the "never fails" comment, since mine did. But, to be fair, I think anything is prone to failure given enough time and use.

 

^Yep, I have a feeling the newer ones are probably a better design and also aren't as old so they will be less failure-prone. But they can still fail.

Dale

 

This is too technical and over my competencies, unfortunately. Plus, I do not have a Datalogit.

That is some great information. I will look for a '93 CPU #2. Thank you!

I'm not even sure '96+ will fit directly, so I will forget that idea.

High, bouncing idle issue: I came to a complete halt. No more idea, no replacement part on its way.

 

Did you get the fuel rails to seat correctly? If the fuel rails are not seated correctly, it will cause a large vacuum leak and a high or bouncing idle.

Stock ports? Street port? If it’s not stock port, then tuning may be next to get the idle right if the port is large enough.

So idle did not get better when you unplugged the ISC? Air bleed screw below the throttle body is 1/2 to 3/8ths turn open? Once the engine is warm, what’s the lowest you can bring the idle down before it dies?

Matt

 

I think secondary fuel rail is correct (I took a picture just before installing the 2 bolts). It was like that before I took it off.

Street ported.

I just tried to unplug the ISC this morning. ISC plugged or not, it makes no difference at all. No change in idle, absolutely nothing (idle is at 1,600 RPM).

Lowest I can get the RPM is 1,600 RPM (when it is warm). I can get it much lower when it is cold.

Under 1,600 RPM, it bounces from 1,100 RPM to 1,600 RPM.

 

In the settings in the Commander is an Idle IG control. Is that on or off?

It sounds like the ISC is just flat out non-functional, could be bad wiring or something. May want to check resistance. I guess in theory it could be something with the driver for that circuit in the PFC but that's uncommon.

I do want to say that I read something about someone modifying a stock harness and removing the plugs for the solenoids, and in doing so they basically cut the power wire for the ISC. Don't know if that's possible.

Dale

 

Idle IG Control was set to YES, I tried to play with it and set it to NO, no change whatsoever.

I've got a new single turbo harness, so I'm buying the idea of bad wiring. But I do not know how to test everything.

I already removed the ISC, cleaned it, and tested it with a battery.

PS: I just tested the clutch switch and it works fine.

 

Just looked it up, the ISC has 2 wires going to it, black with white stripe and blue with green stripe.

The B/W wire is 12v with key on. That's a common 12v that goes to all the solenoids on the engine.

The blue/green stripe (in Mazda it's L/G) goes to pin 4Q on the ECU. The ECU pulses that wire to ground to make the ISC operate. More pulses, it opens wider, higher idle. Less pulses, opens less, lower idle. You really can't see this with a multimeter, you'd need an oscilloscope to see this and that's beyond what you would really need for troubleshooting. Make sure you have continuity on that wire back to the ECU.

Dale

 

I'm keeping that in mind but right now I've got some major development.

BOUNCING IDLE IS FIXED!

TB coolant was bypassed before I began this whole rebuild story. However, I connected both coolant lines to the TB after the rebuild.

Now, I have just bypassed it again. It fixed the bouncing idle, and the high idle is now 1,200 RPM instead of 1,600 RPM. Who would have thought? I still need to go over VTA1 and VTA2 specs (but it is much closer to be OK).

I'm about to reinstall the turbo, but I cannot ignore the fact that the idle still drops a LOT when I spray brake cleaner or starting fluid at the LIM to engine block gasket. This is the last step before going for a test drive.

 

It was me! haha! In cutting the wiring for the solenoids I also cut the black with white stripe wire that gives power to the ISC.
Quick and easy way to check for this should be to just probe the ISC connector and see if you've got +12V with the key ON. Not sure of how the OP's wiring harness is done, but again, quick and easy test if you've got a multimeter handy.
You might also be able to read something from testing the other, pulsed ground signal at the ISC connector if you put the meter in Ohms and try to measure the resistance from the pulsed pin to chassis ground. If it reads as overload you have no signal so either the connection to the ECU is broken or the ECU isn't pulsing the line like it should, if it reads close to zero you may have a shorted ground or an ECU problem. Just another thing to try.