Howell TBI extra port on Throttle Body - JeepForum.com
 
LinkBack Thread Tools
post #1 of 14 Old 08-21-2017, 01:10 PM Thread Starter
86renegade
Registered User
1986 CJ7 
 
Join Date: Jun 2016
Posts: 181
Garage
Howell TBI extra port on Throttle Body

I've finished the install of the Howell TBI on my 86 cj-7 but there is still a port on the throttle body that has nothing connected to it? I've double checked the vacuum schematics and I don't see anything that gets connected to this. It is labeled port "S" it looks like?

Heres a picture of it:




EDIT:

I was trying to decrease my idle RPMs and couldn't seem to get it lower than 900. Then I noticed an open port, if you look at the picture above: Just below the base of the throttle body there is an open port just to the left of the EGR. When I put my finger over this valve I could feel vacuum being draw in and if I blocked the port with my finger the engine would begin to stall. I've hooked the open port on the throttle body to the open port to the left of the EGR valve and my RPMs are now exactly where they are supposed to be! Anyone know if these two ports are supposed to be hooked together? I can't find anything about it in the Howell install instructions

86renegade is offline  
Sponsored Links
Advertisement
 
post #2 of 14 Old 08-22-2017, 03:28 AM
gmakra1
Registered User
 
Join Date: Jun 2016
Location: Tellico Plains
Posts: 229
I dont recall a vac port there from when I did my Howell.
Why dont you call Troy at Howell.
gmakra1 is offline  
post #3 of 14 Old 08-22-2017, 09:10 AM
STJP
Web Wheeler
 
Join Date: Feb 2014
Posts: 1,432
Post

Be careful of my advice. I am no expert on TBI or any other part for that matter. With that disclaimer.....Could the port at the bottom of the TB go to the PCV?

The port you refer to at the left of the EGR in the picture usually goes to the distributor vacuum advance on carbureted 258s. The end of the fitting is blocked with a bolt in your picture as that port would go to the brake booster if you had power brakes.

In this picture (I pirated from somewhere and I know it is not a TBI) the yellow vacuum line goes to the distributor, the port with red arrow is to brake booster (blocked in your case). Not easy to see, but note the vacuum line from the bottom of the carb going up to the PCV.

My help is self-serving as I plan to install a Howell TBI soon and want to maintain the EGR. Figure it out so you can tell me

JS
Attached Images
 
STJP is offline  
 
post #4 of 14 Old 08-22-2017, 05:08 PM
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert
Posts: 18,770
The one labeled "S" is likely a ported vacuum source for certain emissions systems. Depending on your setup, you may not need it, so just cap it.

The other port, left of the EGR in your pic, is a manifold vacuum source. It can be used for certain equipment that requires a manifold source, like a brake booster or TAC system. Again, if your setup doesn't use it, just cap it.

Always cap any unused vacuum ports.

Matt


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Matt1981CJ7 is offline  
post #5 of 14 Old 08-22-2017, 05:34 PM Thread Starter
86renegade
Registered User
1986 CJ7 
 
Join Date: Jun 2016
Posts: 181
Garage
Quote:
Originally Posted by Matt1981CJ7 View Post
The one labeled "S" is likely a ported vacuum source for certain emissions systems. Depending on your setup, you may not need it, so just cap it.

The other port, left of the EGR in your pic, is a manifold vacuum source. It can be used for certain equipment that requires a manifold source, like a brake booster or TAC system. Again, if your setup doesn't use it, just cap it.

Always cap any unused vacuum ports.

Matt
If I cap the manifold vacuum source my jeep has problems running, hard to start, iffy idle
86renegade is offline  
post #6 of 14 Old 08-22-2017, 09:15 PM
Rtracy2001
Registered User
1985 CJ7 
 
Join Date: Oct 2013
Location: Blackfoot
Posts: 28
Quote:
Originally Posted by 86renegade View Post
If I cap the manifold vacuum source my jeep has problems running, hard to start, iffy idle
It needs to be capped. Uncapped like that you are drawing in dirt and artificially leaning the mixture. Once you have the TBI set up and running, it should automatically reset/adjust the idle air control valve to let the engine idle properly. (engine warm, run >45 mph for about 5 minutes, and then come back to idle. If everything is hooked up right, the computer does the rest.) I hope you haven't played with the base idle adjustment.

the "S" port is for the canister purge IIRC. The large port is the PCV valve. There should be another smaller port for the EGR valve and vacuum accessories (during the TBI years, GM used vacuum to control most of the heater/vent blend doors).

My luck is so bad, if I bought a cemetery, people would stop dying.
Rtracy2001 is offline  
post #7 of 14 Old 08-23-2017, 01:32 AM
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert
Posts: 18,770
If the ports aren't being used, cap them. Period.

Are you running ported vac to the dual CTO, and then on to the canister purge signal and EGR, like the Howell instructions outline?

Matt


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Matt1981CJ7 is offline  
post #8 of 14 Old 08-23-2017, 01:15 PM Thread Starter
86renegade
Registered User
1986 CJ7 
 
Join Date: Jun 2016
Posts: 181
Garage
Quote:
Originally Posted by Matt1981CJ7 View Post
If the ports aren't being used, cap them. Period.

Are you running ported vac to the dual CTO, and then on to the canister purge signal and EGR, like the Howell instructions outline?

Matt
Yes, i have all the vacuum lines run exactly how the Howell instructions say to connect them. If i need to cap it then what do i do about the jeep not cold starting when the port is capped?
86renegade is offline  
post #9 of 14 Old 08-23-2017, 01:25 PM
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert
Posts: 18,770
I'd call Howard, if the computer doesn't train itself, as stated above.

Matt


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Matt1981CJ7 is offline  
post #10 of 14 Old 08-23-2017, 02:03 PM
STJP
Web Wheeler
 
Join Date: Feb 2014
Posts: 1,432
Renegade,

A related question....I plan to install a Howell on a newly rebuilt 258.

When you first installed the Howell and had checked connections etc etc, how quickly did you have the engine running. Did it fire right up and run? Of course it probably did not run perfect, but could you run it around 2000 rpms?

JS
STJP is offline  
post #11 of 14 Old 08-23-2017, 05:23 PM Thread Starter
86renegade
Registered User
1986 CJ7 
 
Join Date: Jun 2016
Posts: 181
Garage
Quote:
Originally Posted by STJP View Post
Renegade,

A related question....I plan to install a Howell on a newly rebuilt 258.

When you first installed the Howell and had checked connections etc etc, how quickly did you have the engine running. Did it fire right up and run? Of course it probably did not run perfect, but could you run it around 2000 rpms?

JS

Once everything was installed(took me about 15 hours over three days) I went to turn the engine over and the starter solenoid would spark and the wires on the solenoid from the new Howell kit would get very hot.

I unhooked my battery and the wires on the starter solenoid and then re-attached them all and the jeep fired right up, it seemed to learn pretty quickly as the idle smoothed out very quickly. I haven't had a problem since other than this extra port I'm currently trying to figure out.
86renegade is offline  
post #12 of 14 Old 08-23-2017, 05:27 PM Thread Starter
86renegade
Registered User
1986 CJ7 
 
Join Date: Jun 2016
Posts: 181
Garage
Quote:
Originally Posted by Matt1981CJ7 View Post
I'd call Howard, if the computer doesn't train itself, as stated above.

Matt
How long do you think I should give the ECM to learn with the port capped? Should I unhook the battery to reset the ECM, then plug the port and re-attach the battery cables to have the ECM learn fresh with the port capped?

I've called Howell about the open port on the throttle body and they said it can be capped as it is not used with my year of jeep and that the throttle body is one they use for multiple applications and not all the ports will be used for every setup. The guy I spoke to at Howell said the same thing about plugging the port on the intake manifold.
86renegade is offline  
post #13 of 14 Old 08-24-2017, 03:15 AM
gmakra1
Registered User
 
Join Date: Jun 2016
Location: Tellico Plains
Posts: 229
It learns pretty quickly like 10 trips but it takes 50 trips to lock in all th new data.
gmakra1 is offline  
post #14 of 14 Old 08-24-2017, 03:31 AM
Matt1981CJ7
Web Wheeler
 
Matt1981CJ7's Avatar
1981 CJ7 
 
Join Date: May 2011
Location: Elbert
Posts: 18,770
Quote:
Originally Posted by 86renegade View Post
How long do you think I should give the ECM to learn with the port capped? Should I unhook the battery to reset the ECM, then plug the port and re-attach the battery cables to have the ECM learn fresh with the port capped?
That seems like a logical approach to me, but I'm certainly no FI expert. Again, that would've been a good question for Howell.

Matt


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Matt1981CJ7 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome