89-91 Nonturbo emissions removal

Note that on this engine, your 6 ports and VDI are controlled by your air pump and emissions solenoids/rack. I don’t really recommend removing all this, it doesn’t create a ton of room anyway. IF you remove these parts, you’ll have to come up with another way to make your ports function, or you’ll lose power. This writeup assumes that you’re also going electric 6 ports/vdi. There is a writeup elsewhere on the page about this. Also note that on this engine, you have idle problems much of the time, even before emissions removal. Because of this, I always leave the BAC valve in place to help out. You don’t have to have the coolant lines run to the valve for it to work.
When I refer to emissions removal, I generally get rid of everything on the engine not needed to run, even though they may not be emissions parts. Some of these parts can be left in place while others are removed, but this writeup shows you everything that can be removed while maintaining the running of the engine. Some users may want to keep the cold idle thermowax and coolant lines. I find that a healthy engine with properly adjusted idle (I sometimes bump mine up to 1000 or so) has no problems running normally without this. You can also remove your oil metering system and run premix at this time for even more simplicity, but I don’t normally consider this part of emissions removal.
You’ll need plenty of vacuum caps in sizes 5/32”, º”, and 3/8”. Also a tube of ultra black sealant or equivalent (permatex), blockoff plates, 5/16” fuel injection fuel line (about 5 foot), hose clamps, and a few feet of 5/32” vacuum line and some tees/splitters. I use jb stick weld, not the liquid kind, but the putty type that you mix with your fingers, for the holes left in the TB by removing the throttle plates. Some more paranoid individuals might wanna take the extra time to tap and use metal plugs instead, though I’ve never had an instance where the jb weld came out of the hole (I pack it in well, and leave a lip on each outside edge).
Start off by removing the upper intake manifold. Then remove the vacuum rail and associated parts. For help with this part, refer to the engine teardown procedures listed elsewhere in the tech section. The engine should look like this when you’re ready to proceed here.

Now is a good time to pull the LIM and check/repair your 6 ports if they are sticky or locked up.
Install the acv blockoff plate, with a new gasket and rtv. When installing plates, use vise grips (or the double-nut method) to remove the studs, and use bolts for the plates for a cleaner look. The acv plates leak very easily, so be sure to seal this one off very well. The upper lefthand corner is where the leaks occur. Also put caps on the 3 nipples on the LIM, one of which is over by the fuel injectors.

Assuming you’re removing the thermowax and associated coolant lines, we’ll block off these coolant ports. To do so, I drain the coolant (obviously). I take the tube of ultra black sealant (this stuff dries very strong) and inject some into the nipple, enough to penetrate all the way down. Then I take the large vacuum cap, and inject a little into it as well. Put the cap on the nipple, and use small hoseclamps to tighten it down. Don’t refill the coolant for a couple of hours, to give the sealant time to dry. The sealant is important, the vacuum caps are not rated for high heat or pressure, but the sealant keeps coolant from making it’s way to the cap (or much of it, anyway). The cap keeps the sealant from being pushed out of the nipple, or developing a leak. I use these on my own cars with no issues, but you may want to check and replace them about once a year.

Now I install the fuel rail, injectors, and wiring back onto the engine. Now is a good time to check and clean your injectors, replace grommets and orings, etc. As for wiring, you’ll connect all 4 injectors, CAS, the green coolant temp sensor under the alternator, the 02 sensor, and the temperature probe under the oil filter. Clean off one of the mounting pads on the rear rotorhousing with a wire brush or sandpaper, and clean the wiring harness ground ring, and bolt it down securely. You may want to run additional grounds to this point as well. Everything else can hang loose, it won’t be used right now. Note that I’ve reinstalled the oil tube vent hose on the drivers side of the engine, which goes to the firewall. When leaving this in place, you can use a vacuum cap to seal off the unused nipple on the oil tube above it…or, you can leave that nipple open (vented, or run to a catch can) and seal off the lower nipple (that the hose goes to) with a cap. One of the 2 must be vented.

Run a new supply fuel line with a new hoseclamp. This goes directly to the fuel filter.

Assuming youre keeping your OMP intact, run the 4 oil injector hoses to a vacuum splitter, and run a 12” length of vacuum hose out the back of the engine to be connected later.

Now install the middle intake manifold. When reusing an old intake gasket, I use a little bit of rtv smeared on the upper surface to ensure a tight seal.

Cap off the unused vacuum nipple toward the back of the passenger side, under the BAC valve…

Hook up the intake air temp sensor, and cap off the unused vacuum nipple on the front/drivers corner of the manifold.

Using vacuum hose and a tee, connect the fuel pressure regulator to vacuum, leaving an open port for the pressure sensor. I’ve also run a new fuel return line, using a new clamp, from the secondary rail/fpr. This goes directly to the firewall connection.

I enlarged the hole in the ring terminal for the harness ground (that used to bolt to the vacuum rail) so it could be bolted down.

Go ahead and connect the pressure sensor to the vacuum tee, both secondary injectors, and the BAC valve, and 02 sensor.
Cap off unused nipples on the upper intake…

Large cap on the AWS hose nipple…

Throttle body mounted in vise, TPS up…

Remove secondary throttle plate actuator and bracket…

Throttlebody flipped over, thermowax up…

Remove thermowax (this also removes the bracket for cruise control, so this cant be used either).

Remove dashpot and bracket…

Remove Fast idle cam and spring (you have to remove the throttle stop plate while holding the throttle pullies back, then remove the snapring, cam and spring, and replace the throttle stop plate and screw)

Now mount the TB in the vise with the butterflies facing up. Remove the Top set of butterflies and shaft, and plug the holes with jb weld, leaving a lip on each outside edge so they can never move. Don’t let a lot protrude into the intake path.

Install TB and UIM. Reconnect TPS.

Plug or cap the extra hole left on the intake tube..

I drill a small pilot hole, and use a plastic or metal coupler inserted in the hose to the BAC valve for the air for the oil injectors (the hose we ran previously). You can put this hose anywhere between the airflow meter and throttle plates, though.

IF you plan to do electric 6 ports/vdi, go ahead with that now. When you’re done, refill your coolant and crank it up. Expect to have to hold your foot on the gas for several seconds or a minute, for the engine to warm up enough to run on its own.