Top of throttle body.

[Paul Higg]

Can anyone tell me what the area under the rectangular plate on top of the throttle body is for, what it does? It does not explain that in the FSM.

Thanks.

Paul

 

[G Winter]

I had that off on my 90 and just found a vacant area. I think it is just a place for a name plate.

Glenn

 

[Paul Higg]

Did you see my photos in a previous post today? Oil everywhere. It was a mess.

Paul

 

[topless82vette]

Did you see my photos in a previous post today? Oil everywhere. It was a mess.

Paul

If its like a TPI throttle body there is in fact vacumn contained by the lid and gasket. I know it does draw PCV gases from one of the valve covers so that could explain the oil mess.

 

[topless82vette]

If its like a TPI throttle body there is in fact vacumn contained by the lid and gasket. I know it does draw PCV gases from one of the valve covers so that could explain the oil mess.

I should have mention its the larger hose fitting on the passenger side the top hose fitting. On mine it looks like it draws whatever comes from this hose into the front of the throttle body where the throttle blades are. there is also a small port under this cover that exits right behind one of the throttle blades .
Hope that helps.

 

[So Bay Vetter]

If its like a TPI throttle body there is in fact vacumn contained by the lid and gasket. I know it does draw PCV gases from one of the valve covers so that could explain the oil mess.

That is exactly the exlpination. As it was explained to me, the oil is from compression/back pressure (ie-High RPM or letting off or down shifting at high speed). It pushes oil into the vent tube which, in turn is drawn by vacuum into the TB. On my 96, it deformed the rubber gasket seal under the top plate.

 

[Paul Higg]

Excellent! Thanks guys! Did you see my photos in a previous post? It showed all kinds of oil and a REALLY deformed gasket. That was an excellent explanation which is about to go into my Vette files.

I appreciate it.

Paul

 

[vetteoz]

On mine it looks like it draws whatever comes from this hose into the front of the throttle body where the throttle blades are.

Should be no oil there if PCV system is working correctly.

Unless a LT1 is different from a L98 ,that is a SUPPLY port for the PCV system;
Air goes in pass side cover, out PCV valve in drv side cover ( or in the case of a LT1, drv side of intake , ) to intake.
There is no vac on that port, but vac on the lower one for charcoal canister purge.

 

[Paul Higg]

I do not know about that. According to Junk he said that is normal and he even said he likes it! He said it is one way for the valves to get oil from the top!

Paul

 

[vetteoz]

According to Junk

Should know by now , not to believe everything you read online.

Little test for you.
Start engine , remove your "supposed" vacumn line from the top port on the TB , put finger over hole and see how much suction there is.
Then do the same with line that goes from PCV valve to intake on the drv side .
Report back findings.

 

[Paul Higg]

Well I do not have the time to do this. Please tell what I would find. Did I do or say anything wrong? If so I am sorry if I got it wrong and might have messed people up.

Paul

 

[vetteoz]

Please tell what I would find. Paul

I'm interested to see ; maybe the PCV system on a LT1 flows the opposite way to other engines.
Usual setup is to have PCV valve closest to vac source

 

[Paul Higg]

Well, that black plastic tube that sits in the right valve cover and connects to the TB via a hose. I would assume the TB sucks from it because there was a bunch of oil in the top of the TB as indicated by my photos and corroboration by others. Junk told me it is smog related.

 

[toptechx6]

vetteoz is correct, the plastic line to the throttle body is the fresh air supply line to the crankcase on an LT1, airflow is from the throttle body to the valve cover. The PCV valve is on the other side of the intake manifold under the fuel rail cover, consult your FSM section C13, book two for verification.
Oil in the top of the throttle body indicates problems with the PCV system or excessive blowby.

 

[vetteoz]

I would assume the TB sucks from it because there was a bunch of oil in the top of the TB as indicated by my photos .

I would start by checking that the PCV valve is not blocked. Remove from the rubber grommet and shake.If it don't rattle , then try soaking in something to clean it.
Something is wrong if oil is flowing the wrong way against the vacumn.

 

[Paul Higg]

I do not think the PCV valve itself is bad as I just replaced it. I am talking about the plastic tube which is about a foot long directly under the right fuel rail cover which connects to the pipe on the throttle body and connects to the valve cover.

 

[vetteoz]

I am talking about the plastic tube which is about a foot long directly under the right fuel rail cover which connects to the pipe on the throttle body and connects to the valve cover.

As said , check it out.
With engine running at idle, you should have suction on that HOSE , not on the TB supply port it connects to.
If you pull the hose off the PCV valve , you should have suction on that as well.

 

[Paul Higg]

vetteoz, I really do not understand what you are asking. Maybe I am dense but we need to get our parts right. I have an LT1, on the driver's side under the fuel rail cover is the little shiny PCV VALVE with the ball in it that rattles. THEN, under the RIGHT fuel rail cover there is a hole in the valve cover with a rubber seal around it and in it goes a foot long plastic tube which connects to the upper tube on the throttle body via a hose and a clamp.

So, you are saying to remove the little piece of hose that connects to the upper TB and with it in idle I should feel suction on the HOSE itself that connects to the pipe which connects to the valve cover which connects to the leg bone etc...:L

If THAT is the case, then how did all that oil get in the top of the TB? This is contrary to what Junk and several others have told me about their LT1's. I cannot try it now as it is getting late, 12:09 PM EST, I may go to bed soon, the wife is already in bed.

Paul

Paul

 

[vetteoz]

So, you are saying to remove the little piece of hose that connects to the upper TB and with it in idle I should feel suction on the HOSE itself that connects to the pipe which connects to the valve cover which connects to the leg bone etc...:L

Exactly , that hose SUPPLIES air to the pass side cover; not from it.

how did all that oil get in the top of the TB?

Consider this,
the area under the TB top plate which is connected to the port in question is open through a hole to the FRONT of the butterflies. It does not see vac.

However ; under accel when there is little vac in engine to pull air through PCV valve , there is the possibility of excess crankcase pressure blowing oil out of the rocker cover and back up the RH hose you mention to the TB.
Refer to toptechx6 post # 14

 

[Paul Higg]

Okay so what does that mean? Will I need the engine overhauled? If so I am in deep trouble.