Searching for vacuum leaks after intake manifold removal
 

I'm on a bit of a time crunch, so I'll be searching for the next couple of hours while this post is running. Just removed and re-installed the intake manifold, installed Pineapple Racing Aux. Sleeve inserts, rebuilt my OMP, and replaced my fuel filter. After putting everything back together, it's not running right (of course).

All the electrical connections are where they should be, throttle cable seems fine, and the vacuum hoses appear to be where they need to be. What I need to know is what is the best way to diagnose vacuum leaks on an FC. Also, is there any special procedures that need to be done when re-installing the manifold, or the throttle body?

Maybe you've been in my shoes. Maybe, just maybe you know what my problem is. While I'm browsing old posts, feel free to think about my car.

1988 RX-7 Vert. 5-speed, PS, AC, all smog installed and functional.

At start up it revs to 3k. This is normal, I just thought I would share.
Once it hits 3k, it slowly drops to 1krpms, and then drops to 0rpm very quickly and then dies. I can manually hold it alive with the pedal, but I can't look under the hood and keep it running.
While I rev it manually to keep it alive, I tried revving it up to see if it'll go higher. Won't rev past 3.5Krpm in neutral.
I let it warm up with me holding it at 1.5krpm and the idle stabilized a little bit. I tried to drive it around the block, but no luck. Using the pedal under load makes it rev and drive fine until 2krp, but then it starts cutting out BAD. Like a massive misfire/bad ignition timing.

If you know where I should start, please chime in.
If you have tips for vacuum leak finding, chime in as as well.

I will mail a bright shiny American quarter to whoever solves my problem.

Thanks in advance.

Be sure everything is bolted down properly. Did you use new gaskets? Spray WD40 over the engine when it is running, if the rpms increase, you sprayed over a leak. Did you mess with the throttle cable?

Two new gasket, one at the manifold to block, and one at the UIM to LIM. Throttle cable was disconnected when the UIM/Dynamic chamber/Throttle body section as removed as one piece.

It almost sounds like you left off the hose the comes off the intake duct b/t the afm and the throttle inlet. You know, that one inch tube at the bottom of the intake duct that feeds a metal tube on the top aft side of the dynamic chamber that connects to the air bypass solenod and bac?

Or the brake booster feed line on the aft side of the intake manifold is off.

Another hard to find hose when everything is bolted on is the one at the top of the lower intake manifold, that's hidden once you bolt on the upper intake. Also, make sure you have the hose on between the Boost sensor and (I think) above the ACV. Finally double check the vacuum hoses at the back and driver side of the throttle body.

So, to update the thread and give a sense of closure (something lacking in threads you search for. Just half figured out threads.) Here's what worked for me.

I found a leak when I sprayed the top of the fuel rail with carb cleaner. Everything else was solid. I pulled the upper manifold back off, and found an exposed vacuum nipple in the lower intake right where it meets the block, that went up to the three lines on the side of the throttle body.

Put the hose back on, and resealed everything, and it runs like a top.

Thanks for the help everyone.

Similar problem
 

So im having a similar problem and I dont get what you guys mean by "spraying it with dw-40 or carb cleaner?"

I know the general area (Intake manifold) but if i spray it with wd40 what will i be hearing/looking for?

thanks
Aure

Grab a can of Carb cleaner and spray around the base of the manifold, and where the UIM meets the LIM. If the RPS's start to surge and rise, then you've found a vacuum leak. If not, move on to all the vacuum hoses on the manifold. If you spary them, and still nothing try spraying under the UIM. That's where my exposed line was.

Also, the engine not idling was a vacuum problem. The engine cutting out above 1.5kRPM's was a stuck plunger on my throttle position sensor. I got it unstuck, but sometimes while I drive it will stick shut and I have to pull over and un-stick it. Check the little black plunger box on the front side of the throttle body right under where air goes in. With the car off, open the throttle all the way by hand and make sure the plunger has full rnage and doesn't get stuck.

Hope that helps.

Yes it helps kind of. Its just that Im having this problem with a 12A but I should be able to do the same thing.

Im having same exact problem and machanic said it could be a leak so imma check it out.

thanks again
Aure

If it's a carbed 12a, just start sparying around the carb, and the manifold. Anywhere you see a small runner line, spray it. Good hunting.