Leaking throttle body boost leak repair <On Vehicle> no gasket, IAC, or ISC removal

[J. Fast]

Throttle Body Rod Thrust Seal Replacement Guide (On Vehicle Repair):

After a long day at the track I discovered I could only boost to 22psi, instead of 30psi when I started. When I performed a boost leak test I discovered a hissing sound behind the throttle body spring. When I sprayed it with soapy water there were bubbles present. When I articulated the throttle lever the resonation would change which led me to the conclusion my throttle body rod seals were blown.

After examining the throttle assembly for a few minutes I was suspicious as to whether or not the repair could be made without removing the throttle body from the vehicle so I began deconstructing the assembly. What I determined is the repair can be made quite easily in about 30 minutes and you need not remove the IAC, ISC. messy coolant lines, nor compromise any of the OEM seals at the throttle body.

1. Remove the throttle cable from the pivot arm and remove the 12mm nut and washer on the firewall side of the throttle body.



2. Grab the throttle return springs with a set of needle nose pliers and slide them off to the right (be careful as the springs have two turns of preload and will un-wind rapidly).




3. Remove the throttle arm and spring assembly.




4. Remove the spring retainer on the throttle position sensor.




5. Mark the position of the throttle position sensor and remove it.


6. Remove the 10mm nut and washer retaining the TPS pivot assembly.

[J. Fast]

7 Slide a small dental tool or pick behind the nylon thrust seal. Articulate the throttle rod with your hand and it will create some space behind it. Remove the thrust washer carefully and you won’t damage it.




8. Take an impact gun with a #2 Phillips bit and remove the throttle plate retainer screws. Put a lot of forward pressure on the screws and impact slowly so you don’t strip the screws or burnish the threads.


9. Rotate the throttle 90 degrees and slide the throttle plate out.


10. Remove the throttle rod by sliding out from the firewall side.


11. Inserta 90 degree pick behind the front lip of the thrust seals and pry them out. (Go slow and you won’t score the aluminum race they’re seated in)


12. Here’s what my seals looked like vs. new one.




13. Next, take some Q-Tips and spray them with Simple Green or Carb Cleaner and clean the races. Wipe down the inside of the throttle body while you’re at it. Make sure none of the remnants of the seals fell down into the IAC/ISC holes. You can blow them out with a spray can of air.



14. Coat the seals with a bit of synthetic motor oil and tap them into place with an 11MM socket. As you’re driving ensure the seals are driven square. Some of the Viton will shoulder on the race as you drive it in. Remove the residual by circling the seal with your finger once fully seated.

[J. Fast]

15. This is how the seals will look once properly seated.
Front:
Rear:


16. Clean all parts removed and reinstall in reverse order.


Last, Boost leak test to the desired boost pressure you plan to run when you’re done. (I was able to hold 50psi of pressure with 2% leakdown at the crankcase with these new seals)
*Note: The dual throttle return springs can be wound in place on reinstallation. Make sure you wind them (2) times. I grabbed them with a pair of needle nose pliers once I spun them twice. I was able to clip them onto the throttle body and hold them in place while I aligned the throttle rod to the spring retaining cover. Make certain you get the guide pin on the throttle rod seated in the spring retaining cover before you tighten it back down. I torqued all the hardware to 7lbs and used BlueLock-Tight.

Tools required to perform repair:
· ¼”Socket w/swivel extensions and 10/11/12mm sockets
· 10/12mm speed wrenches
· 3/8Socket w/swivel extensions and 10/11/12mm sockets
· Phillips/Flathead screwdriver
· 30/60/90degree pick set
· Impact Driver with #2 Phillips bit and 4” extension
· Needle nose pliers
· Peen hammer

Seal Information and MFR translation information: The throttle shaft seal dimensions for this project are: 10 x 14 x 03. The seal you want to purchase is style AO Viton or Nitrile. (Either will work)


Here’s the Manufacturer interchange table for seals. I found a retailer that was local to me,Harwal. As you can see Timken, SKF/Chicago Rawhide, Transcom, NOK, National, ISP, Kaco, and a few other MFR’s all have translating part numbers. If one of these retailers is local to you the seal can possibly be sourced “same day” locally.


Here’s the fuel vapor compatibility information for the seals. The temperature limitations are also listed on the attached pages.




If you’re looking for additional shaft seals for camshafts, transmissions, custom throttle bodies and etc., they have them or can make them.

This seal repair procedure should work for all 1991-2006 versions of Mitsubishi Throttle Body.

Happy Boosting!

Jeremy Ferranti
AKA: J. @ FasTT Motorsports

FYI, I took a sec or two to browse thru the catalog and also found a seal that would work for the leaking thrust seals on the CX Racing Throttle Body. For those of you who have them and you would like seals let me know.

[J. Fast]

^^^ IF YOU CANT READ THIS: Switch your forum style to Blue

[Jimvr4]

Or you can just send your TB to Dbest671. She rebuilds them with Mil spec seals and polishes if you want the bling.

[dbest671]

I would never use an impact driver on the throttle body shaft/plate unless you have something behind the plate for support. I don't even try to get the screws out anymore, I just use a "grab-it". I've bent shafts and throttle plates using a screw driver by hand (no impact or power tools).

The shaft screws are m4x10mm

Also, if I had to use an impact... I would break loose the screws first before removing the springs/spring plate. At least the spring plate will still hold the shaft slightly open against the SAS and help prevent the soft brass plate from bending.

I would just take the entire TB off, it takes about 10 minutes.

[Jimvr4]

The shaft screws are m4x10mm

This is what I had posted two years ago on the other site:

Can't edit my original posting. The correct info for the throttle plate screws is
oval head M4 x 0.7mm pitch x 10mm length. Be sure to put these in with loctite
M4 x 0.7mm x 10mm from McMaster-Carr

[Erron Spalsbury]

Very nice walk through, thanks J!!

[J. Fast]

I would never use an impact driver on the throttle body shaft/plate unless you have something behind the plate for support. I don't even try to get the screws out anymore, I just use a "grab-it". I've bent shafts and throttle plates using a screw driver by hand (no impact or power tools).

The shaft screws are m4x10mm

Also, if I had to use an impact... I would break loose the screws first before removing the springs/spring plate. At least the spring plate will still hold the shaft slightly open against the SAS and help prevent the soft brass plate from bending.

I would just take the entire TB off, it takes about 10 minutes.

I've seen some of your work, good stuff. If you've ever had to set or remove a screw in high density material or lock-tightened you know they snap or strip quite easily with brute force or with high speed. Try to set or extract a screw in that's locked and aged or set in high density material (like trex) and it will snap or strip unless you pre-drill to set it, or use a "grab it" screw extractor for removal. In comes Makita Lith-Ion impact with high tq low speed impact and you need not worry. As long as the correct head is used and you fit the tip to application you don't have to worry about stripped screws and etc. You dont have to put so much pressure on the plate screws that the plate or arm bends. Just enough pressure on the tool to keep the bit seated.

If I wanted to remove my water lines IAC/ISC, and TB it would cost me some more cash for water lines, O rings, a couple more gaskets, and most importantly it would cost me time to fetch and order all that other crap and install it. $10.00 and 30 mins DONE.

You are doing a great service to others by offering rebuilds. Some of us like changing our oil and others would rather pay for the service.

[dbest671]

I've seen some of your work, good stuff. If you've ever had to set or remove a screw in high density material or lock-tightened you know they snap or strip quite easily with brute force or with high speed. Try to set or extract a screw in that's locked and aged or set in high density material (like trex) and it will snap or strip unless you pre-drill to set it, or use a "grab it" screw extractor for removal. In comes Makita Lith-Ion impact with high tq low speed impact and you need not worry. As long as the correct head is used and you fit the tip to application you don't have to worry about stripped screws and etc. You dont have to put so much pressure on the plate screws that the plate or arm bends. Just enough pressure on the tool to keep the bit seated.

If I wanted to remove my water lines IAC/ISC, and TB it would cost me some more cash for water lines, O rings, a couple more gaskets, and most importantly it would cost me time to fetch and order all that other crap and install it. $10.00 and 30 mins DONE.

You are doing a great service to others by offering rebuilds. Some of us like changing our oil and others would rather pay for the service.

I might be misinterpreting your post, but...

I have had half taken apart throttle bodies sent to me, and I've seen what the average person does. Your post makes it seem so easy, but I've seen what people do LOL. Like you, I'm speaking from experience. The funny thing about those shaft screws is I found that some you can break loose with very little effort and other are just "stuck" LOL. Also, most of the time there is a "lip" on the shaft where the screw comes out of the back that needs to be sanded down so you don't catch/rip the seal when you reinstall it.

You don't even need to remove the ISC, you just unplug it. Also why would need to replace the water lines, undo clamps and take off the hoses, there are no o-rings to replace on the FIAV coolant hoses. The only "gasket" that may need to be replaced it just the metal TB gasket.

Don't forgot to clean off the old shaft seal that is seized to the shaft, usually on the spring side, but I have seen them on the TPS side as well. And loctite red for the shaft screws when you replace them .

For the plate, if you forgot how it goes back... the number and lines are on the y-pipe side, at the top. You will want to insert the bottom part first.