Clickpopboom
May 5th, 2013, 09:01 PM
PCM- Powertrain Control Module
TB- Throttle body.
IAC- Idle air control valve. This is a small, electronically controlled pintle valve that opens at idle. This allows air the bypass the TB butterfly so the engine can idle.
TPS- Throttle Position Sensor. This is an electronic sensor that is actuated by the butterfly shaft on the TB. It tells the PCM how much throttle is being applied.
There are a few symptoms that can be pretty annoying but they are pretty easy to fix. Common signs of a bad IAC valve can be very low idle, very high idle, rough idle, and dying on deceleration.
A bad TPS can cause several problems such as rough shifting, high revs between shift points, or even not shifting at all. It can also duplicate the dying on deceleration that IAC can cause. (when the PCM sees 0% throttle from the TPS, it tells the IAC to open)
Tools Needed:
T20 and T30 Torx Bits (on either a ratchet or t-handle)
Flat Head Screwdriver
Can of Throttle Body Cleaner
Plastic Parts Brush (or old toothbrush)
Green Scouring Pad
Rags
Blue Threadlocker
New TB gasket or some gasket maker
Razor Blade or other form of gasket scraper.
Start by disconnecting both battery cables (need both to reset the PCM). Next remove the air hose between the filter housing and TB. Mine was held on by a metal hoseclamp on the airbox side, and a plastic one on the TB side.
Next remove the 3 throttle cables attached to the throttle body. The 2 front-most cables simply slide forward towards the driver's side fender, then they pop off. The innermost cable simply pops off straight towards the radiator. You can see the 3 cables disconnected here:
http://farm9.staticflickr.com/8539/8711299267_5ff2b171a2_c.jpg
In these pictures you can see the heads of the 4 T30 bolts that hold the TB on.
http://farm9.staticflickr.com/8403/8712426920_f9bb931ae1_c.jpg
http://farm9.staticflickr.com/8397/8712425538_65f618fca9_c.jpg
Also in the above picture the shiny copper sensor in the top right is the IAC, and next to it with the large, black connector is the TPS.
Use a screwdriver to release the catches on the two plugs, then pull them out. Next use your T30 bit to remove the 4 torx screws that secure the TB. The heads often fill up with gunk, so feel free to spray them off with your TB cleaner before removing them.
Set the throttle body on your work area and get to work removing the the TPS and IAC. They are both secured by 2 T20 screws. Make sure the heads are clean on these too. If your factory TPS and IAC are still present, be ready for a bit of a fight, as they have a bit of threadlocker on them.
To clean the IAC simply spray it down the the TB cleaner and brush it clean. In my case the PO had replaced it a few weeks before I bought the jeep, so all it took was a simple spray down.
If your Jeep has blowby like mine, the TB can look pretty nasty.
http://farm9.staticflickr.com/8124/8711298551_3682a0e532_c.jpg
Now comes the fun part- spray down and scrub all of the crud off of the inside throttle body. Use the scouring pad to scrub it all away. You can use a screwdriver to actuate the throttle linkage with one hand and scrub with the other. The roughest part of this is the hole that the IAC mounts in. The easiest way I've found is to soak a shop rag with the TB cleaner, then wrap it around the fat side of a 3/8" extension.
After everything is clean you can reassemble with your new parts (TPS in my case). Use your scouring pad to remove the old threadlocker, and and a few drops to the screws. The IAC has a rubber O-ring so it will be a snug fit to reinstall it. When installing the TPS, line up the slot in the TPS with the prong on the butterfly shaft. Twist the TPS to make the holes line up. You wil have to hold it in place until 1 screw is in.
http://farm9.staticflickr.com/8128/8712423454_245f310289_c.jpg
Use your gasket scraper to remove the old gasket from the intake manifold. Be careful not to drop any chunks into the intake. Spread a thin layer of gasket maker on the lip, or use a new gasket.
Cinch down the 4 T30 screws, reattach the 3 cables and plug in the two sensors.
Reconnect the battery. Turn the key to run, then turn the headlights on, then off. turn the key back to off. This thells the PCM to go into relearn mode.
Take a decent length drive that will get you through all the gears and has several stops.
TB- Throttle body.
IAC- Idle air control valve. This is a small, electronically controlled pintle valve that opens at idle. This allows air the bypass the TB butterfly so the engine can idle.
TPS- Throttle Position Sensor. This is an electronic sensor that is actuated by the butterfly shaft on the TB. It tells the PCM how much throttle is being applied.
There are a few symptoms that can be pretty annoying but they are pretty easy to fix. Common signs of a bad IAC valve can be very low idle, very high idle, rough idle, and dying on deceleration.
A bad TPS can cause several problems such as rough shifting, high revs between shift points, or even not shifting at all. It can also duplicate the dying on deceleration that IAC can cause. (when the PCM sees 0% throttle from the TPS, it tells the IAC to open)
Tools Needed:
T20 and T30 Torx Bits (on either a ratchet or t-handle)
Flat Head Screwdriver
Can of Throttle Body Cleaner
Plastic Parts Brush (or old toothbrush)
Green Scouring Pad
Rags
Blue Threadlocker
New TB gasket or some gasket maker
Razor Blade or other form of gasket scraper.
Start by disconnecting both battery cables (need both to reset the PCM). Next remove the air hose between the filter housing and TB. Mine was held on by a metal hoseclamp on the airbox side, and a plastic one on the TB side.
Next remove the 3 throttle cables attached to the throttle body. The 2 front-most cables simply slide forward towards the driver's side fender, then they pop off. The innermost cable simply pops off straight towards the radiator. You can see the 3 cables disconnected here:
http://farm9.staticflickr.com/8539/8711299267_5ff2b171a2_c.jpg
In these pictures you can see the heads of the 4 T30 bolts that hold the TB on.
http://farm9.staticflickr.com/8403/8712426920_f9bb931ae1_c.jpg
http://farm9.staticflickr.com/8397/8712425538_65f618fca9_c.jpg
Also in the above picture the shiny copper sensor in the top right is the IAC, and next to it with the large, black connector is the TPS.
Use a screwdriver to release the catches on the two plugs, then pull them out. Next use your T30 bit to remove the 4 torx screws that secure the TB. The heads often fill up with gunk, so feel free to spray them off with your TB cleaner before removing them.
Set the throttle body on your work area and get to work removing the the TPS and IAC. They are both secured by 2 T20 screws. Make sure the heads are clean on these too. If your factory TPS and IAC are still present, be ready for a bit of a fight, as they have a bit of threadlocker on them.
To clean the IAC simply spray it down the the TB cleaner and brush it clean. In my case the PO had replaced it a few weeks before I bought the jeep, so all it took was a simple spray down.
If your Jeep has blowby like mine, the TB can look pretty nasty.
http://farm9.staticflickr.com/8124/8711298551_3682a0e532_c.jpg
Now comes the fun part- spray down and scrub all of the crud off of the inside throttle body. Use the scouring pad to scrub it all away. You can use a screwdriver to actuate the throttle linkage with one hand and scrub with the other. The roughest part of this is the hole that the IAC mounts in. The easiest way I've found is to soak a shop rag with the TB cleaner, then wrap it around the fat side of a 3/8" extension.
After everything is clean you can reassemble with your new parts (TPS in my case). Use your scouring pad to remove the old threadlocker, and and a few drops to the screws. The IAC has a rubber O-ring so it will be a snug fit to reinstall it. When installing the TPS, line up the slot in the TPS with the prong on the butterfly shaft. Twist the TPS to make the holes line up. You wil have to hold it in place until 1 screw is in.
http://farm9.staticflickr.com/8128/8712423454_245f310289_c.jpg
Use your gasket scraper to remove the old gasket from the intake manifold. Be careful not to drop any chunks into the intake. Spread a thin layer of gasket maker on the lip, or use a new gasket.
Cinch down the 4 T30 screws, reattach the 3 cables and plug in the two sensors.
Reconnect the battery. Turn the key to run, then turn the headlights on, then off. turn the key back to off. This thells the PCM to go into relearn mode.
Take a decent length drive that will get you through all the gears and has several stops.