89-91 turbo engine emissions removal

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, and/or BAC valve (to help with idle under load). 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”, ”, 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 intercooler and 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. Note that in these pics, the OMP system is also being removed, so the oil lines, injectors, and vacuum hoses will be absent. IF you are keeping your OMP, you’ll run those vacuum hoses to the original splitter and then to the original nipple on the UIM, as directed in the s4 t2 emissions removal page found elsewhere in the tech section.

Use the small caps to block off all the nipples on the LIM.

Block off the ACV and SAP. I normally use vise grips or the double nut method to remove studs for valves, then use bolts to mount the plates with, for a cleaner look. Use new gaskets and/or rtv sealant for a good seal. The acv plates tend to leak at the upper left corner, so use care here.

Use one of the ” nipples to block off the unused nipple on the oil filler neck, unless you wish to keep this connected to the charcoal canister (which you can do, via the original hose to the firewall). The upper nipple, by the fill cap, will need to be left vented so that excess pressure doesn’t build in the crankcase and cause smoke. You may want to run an oil catch can, or a drain hose to the bottom of the car, if you get any oil spillage from this vent nipple. Sometimes a turbo with bad oil seals will allow boost to vent into the oil system, and cause it to blow out the vent hole. IF you leave the stock vent hose to the firewall intact at the lower nipple, you can cap off the upper nipple.

ON the s5 turbo, there is an extra nipple at the turbo that must be capped off. This used to be operated by the turbo boost solenoid, but I assume if you’re doing emissions removal you have a straight exhaust, which usually raises boost above the 8psi that the solenoid helped you achieve, so it becomes useless anyway.

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 rails, injectors, and wiring back onto the engine. Now is a good time to check and clean your injectors, replace grommets and orings, and check/repair/replace your FUEL PULSATION DAMPNER. There is a writeup about this on the tech page, this is very important to helping your car NOT catch fire. As for wiring, you’ll connect all 4 injectors, the green coolant temp sensor under the alternator, the 02 sensor, the knock 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.

Assuming youre keeping your OMP intact, run the 4 oil injector hoses to the original vacuum splitter (if you didn’t break it, if you did, use an autozone version) and run a larger hose out from that, about 8” worth. This needs to go back to it’s original nipple, the largest of the ones on the back of the UIM. (this picture is taken from the s4 t2 writeup, for reference)

Go ahead and run new fuel lines. The one from the lower rail will go directly to the fuel filter, the one from the upper rail/FPR will go right to the firewall drain connection. You’ll need to use a new hoseclamp on each end, each hose needs to be about 2-2.5 feet long. Its not a bad idea to check the hose every 6 months or so for deterioration from heat.

Now, working on the UIM, remove the throttlebody, and all the valves from the dynamic chamber

Block off the valves and vacuum ports…

Now to perform the TB mod, which I perform during emissions removal. Mount the TPS side of the TB up, in the vise. Note that the dashpot for the secondary throttle plate is already removed in this pic.

Remove double throttle linkage and dashpot bracket…

Flip it over to the thermowax side…

Remove dashpot…


Cold idle cam and spring. You have to pull back the throttle pullies, remove the throttle stop plate, the snapring, cam and spring, replace the plate and release the pullies.

Mount the TB with butterflies facing up. Remove the secondary butterflies and shaft, and fill in the holes in the TB, leaving a lip on each side so the jb weld won’t ever come out.

Cap off or fill in the unused nipple on the IC pipe (unless youre keeping the BAC)

Now is a good time to pressurize your fuel system and check for leaks. BEFORE installing the UIM. To do so, put a jumper wire in the yellow check connector at the passengers side strut tower. Turn on the key and check the engine bay for fuel leaks.

Reinstall the TB, UIM, intercooler, piping, etc. Connect the intake air temperature sensor on the TB elbow, ground wire, and the TPS connector. Don’t forget to connect the OMP vacuum hose to the back of the UIM (if keeping it) and the brake booster hose. You now have 3 items that need to see manifold vacuum/boost, they will all get teed together and run to the single vacuum nipple left, on the passengers side of the upper intake manifold…these are fuel pressure regulator (upper fuel rail, back side), blowoff valve, and boost sensor (if you have a boost gauge you can tee it in here as well).

Cap off holes on the IC…

Reconnect your throttle cable and refill the coolant, etc. Fire it up, you’ll have to adjust your idle when warm. When cold, expect to have to hold the throttle for the first 30 seconds or a minute until the engine warms up and will run on it’s own (unless you kept the thermowax system). Your idle adjustment (unless you kept the BAC) is on the back side of the throttlebody, under the IC, on top. IN the above pic, if you look just below the 2 capped nipples, you can see the IC shield plate, and just under that, the 8mm locknut and flathead setscrew that is your only idle adjustment.

Injector Information
Fuel Cut Off Switch & Unflooding Procedures
Rebuilt Engine Start Up and Break In Procedures
N/A to TII Conversion
Automatic to Manual Transmission Conversion,

1986-1988 Pulsation Dampner
Airpump 6 PI

Internal Engine Damage
Coolant Seal Fix
ECU Application List
Engine Removal
Engine Teardown: Longblock to Shortblock
Series 4 to Series 5 Engine Swap
Series 5 to Series 4 Engine Swap
Emissions Removal
Compression Check

Cone Filter/Intake Modification
Electric Fan
Electric 6 Port Conversion
Series 4 turbo engine emissions removal
Series 5 turbo engine emissions removal
Water injection treatment for all rotary engines
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