Removal, cleaning and replacement of PT V8 throttle body
From Knowledgebase
Contents |
Tools Needed
- Philips Head Screwdriver
- 10mm Socket Wrench (short & long)
- 5mm Allen Wrench or Socket
- 4mm Allen Wrench or Socket (if totally disassembling)
- #5 Torx Wrench or Socket
Time Needed
< 2 hours
NOTE: Recommended that WD-40, PB Blaster or other agent is used to soak nuts 1 hour prior to disassembly
Area Impacted
Front of Engine – fully accessed without major body or chassis item removals
Rear of Engine – fully accessed with removal of Air cleaner and Box assembly
The Procedure
As noted above, it’s a good idea to soak the area with some WD-40 or other loosening liquid about 30-60 minutes prior to the removal. Some of the lower areas are kind of grungy and may need some time to loosen. I would also allow 10 minutes or so for a similar soak on the Allen bolts you will expose in the throttle body – you don’t want these stripping or sheering off!!
ISV removal
I suggest starting with the three 10mm cap nuts on the Idle Stabilization Valve (ISV) as these are easy to remove and the removal of the ISV shows the next layer. It will also help you to reach the lower nut on the left side which is hidden from easy view.
The ISV cable has a simple compression clip holding it and it easily removes. The hose above it in the photo should only be removed with the mounting section (upper and lower bolts).
- Remove the ISV connector and clip
- Remove the ISV cap nuts (careful… I lost one somewhere… they are #6 caps)
- Remove the ISV and set aside (now would be a good time to read ISV cleaning article)
Step 2
With the ISV removed, you can now more easily access and remove the next items
- Now you can access the lower bolt (indicated with arrow) on the sensor assembly to the left and remove it, with mount. Just pull it aside, do not remove the connection in the boot!
- You can also remove the clip on the assembly below the ISV - again, just pull it aside.
Step 3
Now it's time to pull the intake assembly off the throttle body.
- You can also remove the retaining ring and hose indicated on the right with an arrow (be gentle)
- Remove all 6 bolts indicated with the circles in the photo, feel free to hit these with a penetrating spray if you they have never been off the car. Note that 4 are vertical and 2 are horizontal. Pay attention to where you remove them as they are not all the same length!
- With all of those removed and the previously mentioned bolts, the whole assembly will pull right up and out (gently) - there may be some resistance, but don't force it with tools, rock it gently - remember this is aluminum!
The underside of the assembly looks like this (see thumb) and should have a gasket sticking to it, or still located in the frame of the throttle body. As long as this is out of your car – clean it! If you think far enough ahead (I didn’t) you can probably buy the gaskets from your favorite vendor and replace them as long as it’s all apart. If you didn’t, just make sure they are clean and pliable before you reassemble… clean it with some motor oil and make sure the joining surfaces are clean. If you see any indication of wear - replace it!
Throttle Body Removal
Now that you can see the bolts holding in the throttle body, be sensible and SOAK these two 5mm Allen bolts before you try to remove them. You don't want to strip off the heads or sheer off the bolts!
- Remove them carefully, you don’t want to sheer them off!!!
- Assuming all has gone well, you will have a loose throttle body to lift up and out. Note that there is a rod located below the manifold opening on the right that connects to a yoke on the rear of the throttle body (see arrow on yoke). Because of this you may feel a bit of binding as you pull the throttle body - it needs to be lifted up slightly to disengage from the rod.
- Since I forgot to mention them, there will also still be two hoses connected on the left side of the body… You can remove those too, obviously. You can also see the yoke for the rod on the right rear of the throttle body.
So now you should have a complete throttle body in your hands. Assuming yours will be like mine was, get out your carb/throttle body cleaning spray and soak the thing down. Work all of the valves, springs and rods and wipe off anything you can to get it as clean as possible. Once it is clean you can lubricate it with some WD-40 or lithium grease if desired.
Obviously, if you are just replacing the unit, you don't need to clean your old one now, but you should inspect it to be certain that the throttle body was sticking and not the rod under the manifold. Mine was a bit gunked up and slightly balky, but cleaned up perfectly and moved like new, so I reinstalled it. I had a clean one from another car handy in case mine was too jammed up.
Now it's time to look at the well concealed throttle rod.
Where's that rod?
Once you have completely removed the throttle body you will see a pair of holes and the valley below the manifold wherein lies the throttle rod. The rod end is located in the valley under the manifold, hiding like a snake or something… I attempted to get a decent photo of it by shoving the flash down low but it is hard to get a macro focus on it.
There is a bearing ring located where you cannot see, as indicated by the angled arrow. That bearing is part of a mounting assembly, but can be pressed out. I have that bearing ring thanks to Radek, who crossed it in Canada, and Brian Stauffer, who found it in the US.
According to ETKA, the angled arrow shows the location of the angle bracket holding the above mentioned bearing ring. There is a mounting allen bolt (straight arrow) which needs to be removed to release the bracket, but it seems like it can’t be removed without pulling the whole manifold off. According to Radek's findings, the front end mounting assembly is p/n 077723319G and is over $500 in Canada. The complete throttle linkage (the rod and all) is p/n 077133087A and north of $1000 in Canada. Now the good news. He was able to locate a cross for the bearing in the front mounting from NSK Bearings p/n 698ZZMC3E which was $25 in Canada (Brian found a similar one in the US for even less).
Assuming one could remove it and press in a new bearing they would be good to go. I, on the other hand, have a very limited tolerance homeowner’s association and no bearing press, so I thought I would see if I could loosen the rod assembly by hand with some soaking in WD-40. Yes this is the cheapest option, and I like that, as long as it's also going to solve the problem safely...
Since the rod passes along under the manifold, and connects in the rear of the engine, you need to do some more dismantling to reach the back end of the rod. It connects below the cruise control linkage which many people have already exposed in an attempt to stop throttle sticking. Assuming you already know where this is, you can start dismantling to get there, or read the next step if you don't.
Reaching the back of the throttle rod
In order to reach the rear of the throttle rod you must remove the air cleaner assembly/cover (4 big and 3 hidden Philips head screws – you need a longer screwdriver for the hidden ones), and the Filter Box (2x 10mm nuts with thin washers!!) and then pop up the ignition wire tray that is snapped into the thin sheet metal shelf held in by 3 #6 torx screws.
The picture on the right shows the plug wire tray pulled aside and the torx screws (locations circled) and cover plate removed. The box with arrow is the throttle return spring and cruise control assembly area. The throttle rod heading towards the front of the engine under the manifold is also indicated in the photo.
In my case, the cruise was removed already to try to solve the sticking throttle. This is a common action, but I wonder now if the problem is not related to the poor movement of the spring assembly and not the cruise linkage binding.
Lubing your rod
Sorry, couldn't resist... In order to get the throttle rod to unstick, or at least improve it's full range of travel, you will need to soak the spring area here and the rod at the front of the engine. As you can see in the photos, it is not easy to reach the bearing ring in the front of the engine. I used a long straw and guided WD-40 down onto the whole area around where the bearing should be. At the same time, soaking the whole spring and rotational assembly at the rear of the engine.
Once you've let the penetrating oil do it's thing grab both the front knob end of the rod and the lever spring assembly in the back and work the two of them back and forth (it may take some force) you should be able to free the rod. Mine resisted for a few soaks and then popped free and travels well now. We’re trying to determine the best long term lubrication for these areas now in a list discussion. Suggestions are always welcome!
Reverse all of the above for reassembly ;)
Good Luck!!
