At wits end finding an elusive vacuum leak
 

Spent a whole 10 hours today replacing the upper and lower intake gaskets on my GSL-SE - what a PAIN. The old ones were junk and pretty much bonded to the irons and manifolds - someone siliconed the old upper gasket as well (didn't even replace it by the looks of things). I replaced them as spraying carb cleaner around the injectors and lower manifold gasket the motor smoothed out and idled well. After replacing them, I'm back to square one. Same spot, still leaking.

I'm wondering if the injector grommets may be the cause, as well as some parts for them. They were pretty malleable and not rock hard, seems like they seated ok. Unsure if the "pintle" piece was on there as well as the screen, there is a piece in the irons that has 4 small holes. Replaced the oil injection vacuum lines too as they were rock hard and broken (also broke the plastic vacuum spider piece and joined a few T's together to macgyverr it).

Pretty much lost at this point on what may be the cause in that vicinity. Don't have a smoke machine either, but my work may be able to smoke it.

Replacing the lower intake gasket is a chore as the gasket is ALWAYS stuck to the manifold and to the engine and is terrible to get off. I have never had to replace one on an SE and would never unless I were certain the gasket had failed. Also, ensure that you do not remove the dynamic chamber from the runner set as that gasket is no longer available. Also another gasket that I've never seen go bad in 20 years of RX-7 ownership.

Replacing the seal kit on each injector is a must if you removed the injectors. At this point in the car's life, I would replace the seals just as preventative maintenance. I would also take the time to replace every vacuum line on the engine and to the two solenoids that are bolted to the right side of the firewall.

Have you looked into leaking throttle shaft bushings on the throttle body? The bushings can wear, causing a vacuum leak that can be frustrating to find. I would go through and inspect each rubber hose on the engine for any cracking or loose fitting. Spray the throttle body and see if the idle smooths out.

On replacing a failed 13B engine under warranty-or afterwards,the worst,tedious part of the job was cleaning up gaskets. LIM in particular,in the past I have joked you could drive an SE with all LIM hardware loose/missing and it would run fine due to the heat cycled Bakelite like gasket with its death grip on components on either side

I can’t seem to find the thread,real sure recently responding to a very similar thread about this topic and thread starter posting finding a vacuum leaks in area of LIM and intending to replace that gasket.
I recall instructing op to revisit leak testing to try to pinpoint source of leak just as 1st responder to this thread has. Also recall saying failures of this gasket near nonexistent- except after gasket/engine replacement where hardware left loose or not tightened properly.
Think I recommended to op to renew all vac hose on engine as they can have cracks and spits particularly on their undersides that aren’t seen and sometimes don’t react to leak testing.
Anytime you have the manifolds off these engines after all the years on them the vacuum lines should be inspected closely. Having to go back and find a vacuum leak on a poor idling engine after having it apart for other repairs,requiring disassembling what just put together will sour your day
Like above,I include injector o ring replacement while in the neighborhood.
Op good luck in search and post back findings to benefit future readers of this thread.

Looks like I'll be pulling the upper off and replacing those seals then. I think I recall someone else having a similar issue and found out it was those o-ring gaskets. As far as the throttle body goes, the shaft has little to no play in it. Recently took it off, cleaned it, and lubed it. If that doesn't do it, I'll see if someone could sneak my car in for a quick smoke down.

Yeah, that was me lol. Hind sight is 20/20 and kinda regret it, but at least I've seen the magic behind the 6 port system and a possible freeze plug that is seeping some.

Once its running, spray the throttle body near the throttle shafts with brake clean to see if there's a change in idle. Worn throttle shaft bushings don't necessarily cause the throttle shafts to have noticeable play.

Alright. Changed out those injector seals and it helped it some, but still has some sort of vacuum leak in that are. Couldn't get the top seal pushed up into the rail, not sure if that matters or not? I did notice there is a black canister near the rats nest that I wonder if the line to it may be brittle (didn't have enough hose on hand to replace it). Don't know what else it could be at this point besides maybe the oil injectors (already replaced the vacuum lines to them)? It's only in that specific area where the injectors are at that if you douse in carb cleaner it really smooths out and idles well.

Sprayed it down, didn't make a difference unfortunately.

Check the o-rings on the injector diffusers. I went crazy chasing a vacuum leak and it turned out those seals dried out and cracked. The diffusers are plastic and mine completely broke when removing them, so you might just be better off ordering complete replacements.

Diffusers? I know there's a plastic piece in the injector hole that I assume atomizes the fuel (a few small holes in the tip), otherwise haven't heard that term before. I did replace the lower o-ring seals on the injectors if that's what you're referencing.

Yep,the plastic piece! It has its own seals. Those went bad and were giving me a leak around the lower injector seal.

Oh lovely...

I'm sure Mazdatrix loves my business lol. I'll give that a shot as well as replace all the vacuum lines and see if that'll help it.

Bump from the dead. Replaced the injector diffusers and no difference. Since it's not a daily and kept near my parents, my dad got bored and tinkered with it. Got it running well, but I think it may be idling rich still (he had to richen the idle "mix"). Idle is set around 1k rpm, and slightly bounces if set below that. Still likes to dip to roughly 500ish rpm when depressing the clutch coming to a stop for the first time, afterwards it's ok.

He did some research as well and came to the conclusion that rotaries don't like to idle much or idle well. Not sure how true that is though. Thinking of taking it to our Mazda dealer across the street if they have a tech that knows the older stuff, if not I may see if the RX7 shop in town might take a peek. Also want to smoke it and see if any noticeable leaks are present.

Not looking for perfection, but it just doesn't seem to be running right IMO.

Unless you know the techs at the dealer well, I would skip the dealer. They don't see rotaries much and if they do its RX8s. An SE will be new ground mostly likely.

you might want to go through the procedure for setting the idle speed and mixture, and the TPS. if you have the air pump and ACV working the idle mixture should be in the middle, if you have removed that stuff, the idle mixture will need to be all the way rich

this is a larger problem than most would think, and now that most of the time i'm not working on a DD or customers car, i actually will get the torque wrench out and torque almost everything

I've done that too many times to count lol. Seems like it prefers it richer (bad air pump/ACV?), but not all the way rich. Anything half way or under, it just wants to idle like crap. I did bypass the dual throttle/first set of throttle blades, don't think the diaphragm works.

Yep, back again :P. This time, no vacuum leaks that I could find. Performed standard idle adjustment, and found that it wants to idle on the richer side. I have the idle mix screw turned about 45* past center and idle bleed about 1/4-1/2 turned out from stop and idles alright. I can get it to idle at 800-900 rpm, but it tends to fluctuate slightly. I can hear some random what sounds like soft exhaust backfires from either being too rich or something else (random as in once every few seconds or so). Leaning out the idle and increasing idle air bleed leads to a terrible fluctuating idle. Blipping the throttle, it sounds like it's trying to step the idle down roughly (sounds like you're exhaling hard and closing your lips in succession, but not as harsh sounding). Also noticeable hesitation/surge at roughly 3500rpm. Runs fine otherwise.

Replaced all the hard to reach vacuum lines for the rats nest and others under the upper intake, plus a few others that were brittle and had holes in them. Replaced the brake booster soft lines. Upper and lower intake gaskets and injector o-rings and seals. New throttle sensor (old one was shot). Sprayed down all the lines and gaskets I could think of, plus the TB and couldn't find anything. New plugs, wires, cap, and rotor. Can't verify timing due to missing marks on crank pulley. Mostly original car, if that helps any.

Not sure where to go now. I just want to experience this poor thing run right.

Hesitation, surge at 3500rpm - under load? If yes, that sounds like 5/6 ports sticking from actuators that may not be opening evenly or one not opening at all. These work through exhaust back pressure as sensed through the Main Catalytic Converter. There's a back feed pipe which has a gasket where it connects to the converter, and this sends pressure to the Lower Intake Manifold through a spigot attached to a one-way valve just near the firewall on the exhaust side. At about 3800rpm, under load, there's adequate gas volume (about 4-6 psi) to open the 5/6 port actuators. These each have gaskets that MUST seal, or neither port actuator will work. Any amount of leakage in the port actuator air pressure will prevent them from opening, as you're not dealing with much pressure to begin with.

With properly activating port actuators, you can feel the intake shift to better high rpm breathing - its like a variable cam on a piston engine - and is what makes the SE so much more fun to drive. Flattening out the torque and power curve makes the car much easier to drive fast, too. Remove the port actuator cans carefully, and check the condition of their gaskets.