Other DIY's exist for these tasks, but this guide explains how to replace all three gaskets and clean everything at the same time - which you might as well do if you're going to invest the time to do any one of these tasks. This guide is very detailed: it discusses cleaning and replacing the gaskets in the idle air control valve, throttle body, and intake manifold. It also shows how to disassemble the throttle cable (for those of you with a 2003 or 2004 model).
My car is a 2003 Corolla with ~126,000 miles on it.
Items you need:
Intake gasket (Toyota part # 17171-22060)
Throttle body gasket (Toyota part # 22271-0D030)
Idle air control gasket (Toyota part #22215-7A680)
3/8 drive ratchet
3/8 drive 10mm socket
3/8 drive 12mm socket
3/8 drive extension (3 and 9 inch)
Regular phillips screwdriver
Needle-nose plyers (or similar for removing hose clamps)
2 adjustable wrenchs or 12mm spanners
Throttle body and air-intake cleaner
Let's get started:
These are the gaskets:
Secure the parking break and pop the hood
Remove engine cover (use 10mm socket). If your cover has never been removed, you may have plastic clips holding the cover on. I removed and replaced these with screw bolts years ago. This DIY by JasonA shows you how: https://www.toyotanation.com/forum/13...retainers.html
Remove the duct hose that connects the air box to the throttle body. To do this, you need to loosen the 10mm clamps and pull the duct hose off.
There are 3 breather hoses that connect to the throttle body. Remove them:
Hose #2 (connects to the PCV valve in the back of the engine)
Hose #3 (I did not completely remove this hose, I just disconnected it from the throttle body)
If your Corolla was made in 2003 or 2004, you need to remove the throttle cable.
Use 12mm spanners or wrenches to crack the nuts as shown. I only loosened the top nut so when I reinstalled the bottom nut would still be in place and make sure everything is still set correctly.
When you've loosened the top nut enough, slide the cable out
Remove the electronic connectors on the front and bottom of the throttle body
Remove the bolts from the top of the throttle body (use 10mm socket)
Remove the 4 bolts surrounding the throttle body (use 12mm socket). The top bolts are easy to round off, so be careful. I had to use a bolt extractor.
Remove the metal connector that bridges the gap between the intake manifold and the throttle body. One of the 4 bolts you removed in the previous step holds this part on. Remove the other bolt.
The throttle body should now be only connected to the car by 2 coolant lines (which connect to the back). Slide the throttle body off to get better access to these coolant lines.
Remove the coolant lines. Mine were stuck on pretty good. I used a flathead screwdriver to force them off. Small amounts of coolant will spill when you do this - it's best to have a towel to catch the spillage. Prop them in an upward position so that you don't loose more coolant, or put bolt screws in the tubes (or use similar object to plug it).
Remove the throttle body
Remove the 3 screws holding the idle air control valve (IACV) to the throttle body (careful, these screws are soft and strip easily)
Separate the IACV from the throttle body. You can see the old IACV gasket now.
The black section of the IACV can be removed to allow for a deeper clean. A specialized tool is needed to remove these screws (I've seen it on forums somewhere, but I can't seem to find the link). You can also drill the screws out or use a hacksaw to make an indent (and then use a flathead on the indent).
I replaced these with phillips screws
Remove the old gasket and clean the IACV with throttle body and air-intake cleaner. I used a lot of q-tips. If you remove the black section you can spin the sensor and clean it better. You can also clean the throttle body's butterfly valve at this time.
You can also remove the old throttle body gasket
Remove the intake manifold. To do this, remove the bolts and nuts on the front. There are 5 bolt screws and 2 nuts to remove. You will need a 9" extension for this. There are black clips connected to the intake manifold, but after removing the 2 nuts you can just spin them off to the side.
Slowly remove the intake manifold. As hardtopte72 states in his guide
"When removing take note of the hidden vacuum line behind the intake and remove it."
Take his advice. I've circled the location of the hidden vacuum line. I also circled one of the black clips after it has been unhooked.
Remove the old intake gasket
At this point, I took a significant amount of time to clean the engine (I rarely disassemble the car this much, and it allows easy access to clean the engine bay. I also cleaned the intake manifold and installed the new gaskets.
When you've cleaned everything and installed the new gaskets, it's time to reassemble the car. First, align the intake manifold to the front of the car and slide it back on. Connect the hidden vacuum line in the back.
Then replace all the bolt screws and nuts holding the intake manifold on (there are 5 bolt screws, 2 nuts, a metal connector, and 2 black clips). Reconnect the IACV to the throttle body, and bolt it back onto the car (don't forget the other metal connector). Reconnect 2 coolant lines, 2 electrical connectors, and 3 hoses to the throttle body. Reconnect the duct tube to the air box and throttle body. Verify that everything is reconnected properly. Turn the car on and check for noticeable vacuum leaks. When you are confident that everything is reassembled properly, re-install the engine cover and admire your hard work. Be happy that your car will probably never throw a P0171 code.