This was made known by Sam at RRE and I'm doing this article using content from his post Please read over entire article before proceeding with the bypass For a while there were only a few ways to block the FIAV (Fast Idle Air Valve) so coolant no longer heats up the TB and thus the air charge and also hope to solve or eliminate a suspected part causing idle surge. One way was to buy either a block off plate which eliminated the whole lower portion of the throttle body or you could use a bypass plate. The bypass plate blocked off the FIAV while still allowing the ICS to be used. The lower portion of the throttle body is still used with the bypass plate. The other option is taking the lower half off and just welding everything closed. Now you can safely and effectively block the FIAV for free! I would only suggest getting a true block off plate if you are deciding to eliminate the ICS as well as you will be able to remove the whole lower half of the throttle body. ICS removal is not suggested on a daily driver as you will have cold start idling issues. Tools Required: These tools are required to block the FIAV ● Flat Head Screw Driver ● Mallet (or some other hard blunt object) ● Needle Nose Pliers Other Tools Needed: These tools are to remove the throttle body from the vehicle. Some may or may not be needed depending on current setup. ● Phillips Head Screw Driver ● 10mm Socket ● Socket Wrench in the appropriate size for used socket ● 6" Extension (may or may not be needed) ● Hose Clamp Pliers or some other form of pliers to remove those 3 pronged hose clamps ● Small Flat Head Screwdriver (precision size) ● Towels/Rags New Parts Required: ● Gasket (throttle body to intake manifold) ● Gasket (throttle body elbow [your setup may vary]) Getting Started You should always disconnect the battery when working on your vehicle As stated, your setup may vary and some processes may be different in your case. Removing the battery may help give you more access to the throttle body. To start you will want to remove the throttle body. To do so you will first want to remove the throttle cable from the throttle body (TB from now on). The cable is located on the back side of the TB towards the fire wall. You will need to rotate the wheel counter clockwise to give slack in the cable. Doing so you can then work on removing the cable by lining up the cable end and push it through the provided slot on the wheel. Next you will want to remove any attached vacuum lines on the top of the TB be sure to mark which line goes where if you are still on the OEM emissions setup If you are able to remove your emissions due to not needing to be tested then it will make for a much cleaner look as seen here. Continuing on, you will need to remove the throttle body elbow or the attached coupler depending on your setup. Removing the TB elbow you will need to remove the total of 4 nuts and/or bolts that are holding the assembly onto the intake manifold. Your extension may help here. 4 Pieces to Remove The first is the ICS plug so unplug that. Now unplug the TPS by removing the metal retaining clip from the TPS plug. This is where the small precision screw driver is needed. It works best to push up on the exposed clip end to get the top portion of the clip out of the groove on the backside of the TPS. Once you are able to grip the clip then you should be able to pull it out. If not then work the other clip end out of it's retaining hole and then remove the clip. The clip end is circled in yellow. The last two parts to remove to pull the TB out are the two coolant lines attached to the FIAV. This part may or may not be messy for you depending on if you are careful. The only picture I have available is one with the coolant lines already disconnected and the intake manifold removed. It shows their original orientation as to how they were hooked up at the FIAV. Picture is from the drivers side Now that the coolant lines are disconnected and any spilled coolant has been cleaned up properly, you can now choose your way to remove or dispose of the extra lines. You have a couple choices, you can either loop the coolant lines by taking the longer line and clamping it onto the nipple on the water pipe. Or you can eliminate the lines all together and tap and plug the nipples. I would recommend using JB Weld on the threads when you install your plug of choice on the water pipe and thermostat housing. Onward to the Free FIAV Block off! This is actually the easiest part to do. If you have a 1990 TB scroll down to your dedicated section. Phase 1 As you have the TB in your hand turn it around to view the side that attaches to the intake manifold. You will take notice to a freeze plug located on the lower half. That is the freeze plug that will be removed. To remove the freeze plug, take your flat head screw driver and place it along the inside edge. With the flat head in place, take your mallet or other hard blut object and give the screw driver a whack, or two, or three. Chances are, the freeze plug has never been touched since it was installed when the throttle body was assembled and is stuck in there. All you are trying to do is rotate the half you are hitting downward while the opposite end rotates upwards for you to grab and pull out. 1990 Throttle Body The '90 TB is definitely an oddball seeing as it's a solid piece design and the sensors used only fit on this TB. For you guys that want to reap the free FIAV block need to follow this set of instructions to get to the point we are at now. First turn the TB so the side with throttle wheel is located, you will notice a plug end bolted on. Remove the two screws that attach it to the TB. Underneath will be a round looking plate held in by three screws. Unscrew the 3 screws from the TB and remove the plate. Continue on Phase 2 With the freeze plug removed you will now notice a black circular piece with some indents and a plus sign on it. The piece you are looking at is actually the adjustment for the FIAV as the FIAV is thermostat style valve. When the spring is cold the air way is open allowing for a higher idle. When the spring warms up it will slowly close off the passage way and your idle will will slowly drop down to where it's supposed to be after warming up. One cause for idle surge to occur is when the valve is out of adjustment allowing a portion of air to bypass the throttle plate directly. Disconnecting the coolant lines without blocking off the passage way will not allow the valve to function properly by opening and closing and in it's natural cold state it has the passage open. What you want to do is take your needle nose pliers and insert each end into a dimple as you are going to be turning the adjustment plate clockwise. The 90 TB plate will look like this It may be stiff and a little difficult to turn as you have age with corrosion fighting against you as well as the spring since you are compressing it. You want to turn the adjustment until it bottoms out and can no longer turn. Doing so effectively closes off the airway. No sealants are necessary. Phase 3 Now that you have blocked off the FIAV for free, you will begin the re installation process. First off you need to put the freeze plug back in. Just set it in there and slowly start tapping it with your mallet to allow it to be pressed in the TB. Try to keep it even and if you have a block of wood that will prevent you from dinging up the TB and will allow for a flush fit. 90 Tb Reinstall the plate, it will only fit on one way, with the screws you removed, and then re attach the plug end you removed. Again, no sealant is required but if you feel more comfortable about it, you can RTV the plate before installation. Put Everything Back Together It's going to be the reverse of the removal. Put the new gasket on the intake manifold side and slip on the TB. Next if applicable, put on the Tb elbow gasket on and slip on the TB elbow. Proceed to install the nuts and bolts that your previously removed. Chilton Manual quoted 11-16 Ft Lbs for the 4 bolts, I personally just snug them down. Plug in the ICS, plug in the TPS and don't forget to put the clip back on. Install your intercooler piping back onto the throttle body assembly. Next is the process of re installing the throttle cable. I find it easier to put back on than taking it off. Just rotate the wheel as you did to take it off and take the cable end and start by passing the head through the hole. With that in there, you can just move the cable wire around in the general area to find the slot for it to pass into. That's all there is to it! See, it wasn't hard at all. If you have not hooked your battery back up do so now and anytime you mess with components that see pressure or vacuum you should perform a boost leak test to ensure there are no leaks. No other modifications are required after this has been performed. Your ICS will function properly giving you ECU adjusted idle. Thanks for reading! Scott I wanted to add this in for another potential step. I recently did perform a boost leak test and noticed a minute air leak around the freeze plug. I would recommend putting a bead of RTV around the outside rim of the plug before re seating it and I'm sure a thin layer around the mating area where the plug touches wouldn't hurt either. Also, for those of you that are choosing to utilize a bypass plate be sure to RTV the plate to allow a seal between the throttle body halves and the plate. If you fail to seal it properly, you will likely have an air leak coming out of the coolant passage way. A block off plate can either be RTVd on the mating side or the "o" ring can be utilized if you can manage to get it to seat properly. After allowing adequate time for the sealant to set up, perform a boost leak test to ensure you are not leaking out of the ports or the freeze plug.