I don't know what it is. I own two rx7's and this is stumps me. My 87 TII has had idle problems ever since I restored it last year. Now a new problem's popped up. It'll idle just fine until I give it a little gas (or more) and get some boost. Then after I boost it acts like it has a vacuum leak. The idle goes up, leans out and sometimes surges from 1500-2000 rpms. I've dealt with a lot of vacuum/boost leaks but I've never had one that pops up only after I've used the turbo. Just an FYI, it's got the stock ecu with a fuel cut defender from racing beat and a few other mods (intercooler sprayer, cone filter, aftermarket exhaust etc)

 

Does it stop or do you have to shut it down and restart it?

 

I have to shut it down and restart it, then it idles fine until I boost again. Also it goes away sometimes when I apply the brakes.

 

vac leak.

 

But where would it be? And why does it only show up after boosting?

 

Anywhere that there is a vacuum line.... start the car, spray starting fluid around vacuum lines, wait for idle change.

 

Okay then I have one last unanswered question. Why does the idle change only after boost?

 

Because boost is the opposite of vacuum.

 

Alright, well I found the vacuum leak. It was on the seal around where the wires enter the fuel pressure regulator. Now just to replace it. Thanks for the info. Is there anything else I need to replace while I'm down there?

 

If you've got wires going into your FPR I think you've got bigger issues...

 

well it's a big metal cylinder on the back of the motor. It's coming out from under the UIM and it has two wires going into the side of it. What is it then?

 

And the wire colors are?

 

Aux air valve?

 

Or maybe the BAC.

 

One black and white wire and I can't remember the other one. It's not the bac valve, its brass colored.

 

Pic?

Got me curious

 

yeah, I will upload them tonight. I don't know if it's supposed to be there. The car sat for 9 years and the people who had it before me did a lot of stuff to it

 

Here they are

 

sorry for the bad quality. The wires are black/white and blue/white

 

EGR valve.

 

Are you sure? I thought the egr valve looked more like a dash-pot. This is more cylindrical.

 

So you ask what it is, thinking it's something it's not even close to being, then when someone tells you exactly what it is you question it?

No no you're right, that's you FPR...

 

Injector seals.....

I had exactly the same symptom on a 7M-GTE Supra..

 

 

My S5 has no EGR so no, I'm not sure.
All I did was look at the wiring diagram and find the wire colors you described and it said "EGR".