It has actually started to suck my will to live.

Not really.

So today I went about adjusting my idle and TPS since I'd done all my block off plates yesterday on my 89 TII. I went back and forth over and over trying to get her to stop hunting for idle. Adjust the idler screw, readjust TPS, start car, she'd run a high RPM for about 30 seconds, then drop off to bounce between nearly dead and 1k rpm. After a couple of hours of this my stupid @** finally notices a sucking sound coming from the engine, I'd assumed the changes in vacuum were due to the car hunting for idle, and had been foolish enough to forget that it was more likely the other way around. So I grab a piece of new fuel line since I'm out of carb cleaner to listen for the culprit. I hook the hose around the firewall side of the UIM near the fuel rails and BAM, there it is. I'm going to try some carb cleaner in the vicinity of the sound just to be 100% that it IS in fact a vacuum leak, but the sound was pretty unmistakeable.

I pulled off the UIM just to be sure that there weren't any lines obviously disconnected, there weren't. So if it is a vac leak, the plan is just to replace ever piece of vac hose in the rats nest. Is there anything else that may be more obvious that I'm missing?

/end rant

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/my-screwed-up-idle-thread-epic-617450/

that's something you can read about. That was on a bone stock car. I have been going through vacuum leak issues on 88 T2 with a lot of emissions removal. It really sucks when it's something under the UIM because it's hard to pinpoint.

--look for obviously disconnected hoses of course

--check your injector grommets.

--random gaskets for emissions stuff can leak

I personally use one of these to troubleshoot leaks:

http://www.boostpro.net/prodtester.html

or you can fab up your own. You will need a reducer/coupler to hook it into your turbo. (I think the stock turbo inlet is 2 1/4" , not positive. I have an aftermarket turbo). Then I spray soapy water around the engine bay while I have the car pressurized and look for bubbles. You can also fab up a crossover pipe to replace the TMIC for these tests.

One of the random things I noticed was that if you don't want something to leak under boost you need to make sure you have tight fitting vacuum hose. The air bleed nipples for example could use 3/16" (of course air bleeds do not actually use vacuum), but my pressure tests have discovered that 3/16" leak boost even with a ziptie. You need 5/32 hose because it has a tighter fit. Random things just leak... my IAT was leaking despite teflon tape. I put blue RTV on the threads and it stopped leaking.

You could have a leaking blockoff plate as well. Check your ACV blockoff plate, especially in the upper left corner.

 

First thing I checked was all the block off plates, so those 3 are for sure ruled out. The leak is audible, and definitely coming from under the uim, it sounds like the leak is nearer the firewall side. I will make a point of replacing everything w/ 5/32" line though. I hadn't considered the injector grommets, so I'll go ahead and replace those as well. I really appreciate the advice, thank you.

 

Aaaaand, after finishing the read on J-Rats vac leak from hell, I'm really hoping it's not the same problem for me, Carb cleaner should tell us tomorrow.

 

Carb cleaner says no vac leaks.... still going to replace every vac line and double check to make sure the routing is correct. Basically, the idle is hunting from 300-1100 rpms. The TPS is properly adjusted, the motor had no AWS from Japan, and has since had the Airpump, BAC, Split air pipe, and ACV removed and blocked off. Could the issue be that the solenoids on the vac rack for that stuff is still connected and plugged in? All of the exposed vac lines have been nippled and ziptied, and I'm running out of ideas and patience. Any advice is greatly appreciated.