Last updated: April 19, 2000

Throttle Body Hose Removal

From: Carlos Iglesias
Date: Nov 29, 1998


  1. Remove coolant hose coming from rear end housing at the top firewall coolant inlet on the TB.

  2. Remove the coolant hose which connects the bottom TB coolant outlet to the coolant hardpipe between the oil filter and the oil filler spout.

  3. The hose which was attached to the top firewall coolant inlet on the TB should now be reattached at the hardpipe, completing the rerouting.

  4. Safety wire the Fast Idle Cam FULLY open. The cam is locate on the firewall side of the TB. Failure to do so will not allow idle to fall to its normal speed, since the idle cam is actuated by the thermowax (nomenclature ?) rod, which is immersed in the TB coolant stream.

  5. Coolant plumbing is simplified by this mod.


  1. Regardless of climatic conditions, sufficient idle warm-up to achieve proper engine operating temperatures before cracking the TB will also provide sufficient heating of the TB to assure defreezing.

  2. Post-idle air inlet and engine bay ambient temperatures will maintain TB temperatures above freezing.

  3. Air inlet temperature is only "MARGINALLY" reduced (at best) by this mod.


From: Nick Reifner
Date: Nov 29, 1998

Carlos, you don't wire it 'fully' open. Remember the problem with binding the throttle linkage? I have mine at about 85%. As long as it is opened so there would be no contact if the rod were fully extended, it won't make a difference. I could not get wide open throttle with it fully pulled back. YRMV, but this was my experience.


From: Carlos Iglesias
Date: Nov 29, 1998

Nick, I do remember that, thanks. Being that I haven't had the Double Throttle butterflies for a long time, I will defer to Nick on this. Please amend Spic Racing Factoid #11299801 accordingly.


Date: Sat, 28 Nov 1998 12:19:12 -0500
From: Tom Walsh

I have recieved many request for info and pictures on the throttle body modification.

I will give a brief write up on how to do this and then will go out and take some digital pictures of the mod to post to my web site later on this week.

First off some back ground. The throttle body has two coolant hoses that run to and from the block of the engine. The top hose can be seen easily when you open the hood. It is located on the back top of the throttle body towards the firewall of the vehicle. It is a little bit towards the drivers side of the car and is black in color.(This is the same hose you would use to burp any air out of the coolant system if you needed to.) The other hose can not be seen unless you remove the intake elbow. The hose is located under the throttle body and is a 90 degree bend. It is not easy to get to and this will require the removal of the throttle body to get it off.

Now before you begin make sure you get another manifold to throttle body gasket. Pettit carrys the new metal version of this gasket, and I would make sure you have one handy as the old version breaks very easily. (Note: one make sure you bleed off all presure in the coolant system before you remove either of the hoses.)

The mod was made extremely easy due to the fact that the length of the top hose (the one you can easliy see on the top of the throttle body) is long enough to be routed to where the other hose plugs into the block. Simply take the hose and attach it to the the metal pipe under the throttle body that the other hose plugs into. You must have the throttle body removed in order to do this. It was very easy this way.

Now a word or two about the down side to the mod. After we completed the mod we noticed that the car would idle at 1500 RPMs. Not believing I had a vaccum leak on the motor, I theorize that there is a sensor inside the throttle body that is feeding info to the ECU and telling it that the motor is not warmed up. This has been backed up by the fact that the idle can not be turned down and that the idle will return to normal range after the car has been allowed to heat soak the throttle body. This was verified last night as I had started my car after letting it sit in Brooks' garage and the idle had returned to a normal range. We are currently working on where the sensor is located and hopefully will find a fix for this problem.

Hope this helps. Please check my web site later on during the week to see if I have posted the pictures with this how-to.


From: Rafael Sanchez (
Date: December 13, 1999

I don't know if you figured it out or not, but you can splice the wire going to the throttle body sensor with the engine coolant sensor. This should fix your problem. Good luck!


Date: Mon, 23 Aug 1999 09:20:54 -0500
From: "Westbrook, Chuck E." (

> I had originaly rerouted the hoses to by pass it, but you run into a
> problem with the high idle. There is a termo sensor that determines how
> hot the TB is and opens or closes a second set of butterflies to keep
> the car from going WOT until the car comes up to temp. (or something
> along those lines... I might being combining the AWS and the TB coolant
> sensor) The problem I ran into was the car would only idle correctly
> after the TB had heat soaked... Other wise the car would idle around
> 1500 RPMs which is just annoying...

If you do not deactivate the hot wax rod/fast idle cam unit, then this will cause your high idle until the TB heats up. That hose you removed/blocked off, only has one purpose; to heat up the hot wax rod which in turn slowly moves the fast idle cam from high idle down to normal.

This is in no way associated with the vacuum controlled opening of the butterfly assembly located behind the mechanical secondary butterflies. The AWS only works during startup(can be removed as many have done). The ISC does work along with the hot wax rod/fast idle cam unit for idle control but uses different sensors.


Date: Wed, 19 Apr 2000 12:06:57 -0500 From: "Westbrook, Chuck E." (

> I removed the wax rod assembly (with the warmup rod and coolant
> nipple).
> Can someone explain why Rob Robinette and Jay secured the piece they
> secured?  After removing the wax rod stuff, there doesn't seem to be any
> kind of interference with the fast idle cam.  As far as I can tell, it can
> just be removed completely.  I can't tell what the wax rod stuff is supposed
> to be doing.  The throttle plates seem to open all the way and close just
> fine.  What am I missing?

If you close off or remove the water hose that flows thru the throttle body, then the hot wax rod/fast idle cam unit will not function properly. It has to be disabled. If not, it will keep the revs high because it isn't being heated directly anymore. That is the reason behind securing it open. This prevents it from engaging the throttle linkage.


From: Rob Robinette (
Sent: Thursday, December 09, 1999 8:02 PM

I removed the throttle body coolant flow, here's the How-To with pics:

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