Question About Throttle Body

[GSTwithPSI]

I need to know what all the ports in red circles go to. I was looking for a diagram showing what ports go to what, but no luck. When I mounted my throttle body to the new Magnus manifold, all of these were blocked off by the Magnus manifold flange and gasket (all but the large lower cutout type port). I'm wondering if one of these is needed bypass air at idle?



My real issue is my car wants to stall when the throttle is closed. It idled perfect before the Magnus was installed, so I'm sure the throttle body itself is good. The TPS was calibrated and is good, as is the idle switch. If I bump the throttle open just a bit, the car will idle fine, it just seems like its not getting enough air at idle. I will adjust the biss if I have to, but before I go screwing with it, I want to make sure I'm not missing anything.

 

[manikbastrd]

Big one is the ISC/IAC and FIAV IIRC.

 

[prove_it]

The three small ones lead to the nipples on the top of the body, the big half moon on the bottom is for the IAC and FIAV ports, the medium port in the lower part of your pic is the BISS port.

 

[GSTwithPSI]

Should the BISS port be blocked when bolted to the manifold?

 

[prove_it]

No, I don't believe so. I have four laying at home I'll have to check to be sure.

 

[manikbastrd]

I doubt it, then you would not be able to set your base idle. Is the manifold you have flanged for a 1g TB?

 

[GSTwithPSI]

Yeah, it is. Next question, what are the far limits of the ISC (highest and lowest counts on ECMlink)?

 

[prove_it]

All those ports are blocked with an OEM gasket. The OEM manifold has no holes. I think the holes are there for machining purposes only.

Far counts on the ISC I believe are 0 to around 120, I know I've seen 115 during WOT, so I'd say around that point. 30 is your goal at idle.

 

[GSTwithPSI]

Thanks for that. I'm going to try and get the idle sorted out today.

 

[prove_it]

Are your throttle shaft seals leaking? They will mess you up. Also the O-ring on the biss can leak.

 

[GSTwithPSI]

No, I don't think anything is leaking. Reason being, this TB worked great before the Magnus install. I actually have the opposite problem of a leaky throttle body. The car just idles way too low. I thought that maybe a port that should be uncovered was covered, not allowing the proper amount of air to bypass the throttle plate at idle. You confirmed all those ports are normally closed up, so it looks like I may just need to make a BISS adjustment.

Problem is, I still haven't been able to set the base timing yet, so I need to do that before I start screwing with the idle. I ran into a charging system issue, so I'm sorting that out before I set the base timing. My list of sh*t to do is getting shorter, though. I just did my initial oil change on the new motor, so I'm headed out to the garage to do some more work and get the kinks sorted out. Hopefully by the end of today I have the car in a manageable state.

Thanks for the help!

 

[Wookalar]

Quoting prove_it:
Are your throttle shaft seals leaking? They will mess you up. Also the O-ring on the biss can leak.



Yeah, spray brake cleaner at the TB to see if it idles up. /ubbthreads/images/graemlins/tongue.gif Just messin with ya but yeah TB shaft seals are a source of vacuum leak, IMO it goes without saying that those are just one of those things that needs replacing after all these years.