Port "R" Vacuum? Throttle Body

landtoy80

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• Oct 13, 2004

• #1

On the throttle body there is three ports called P, R, E.
With the motor running I have vacuum at P and E but no vacuum at R.
With motor off I can hardly suck /blow through it. I put a vacuum guage on it and pump it, there is resistance but it doesn't hold vacuum.
Is that port clogged or should there be some resistance on that port?

 

semlin

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• Oct 13, 2004

• #2

all three ports have the same sized exit innside the TB. it is clogged and it means your egr is not working properly. it can be tough to clear. comrpessed air or a stripped twist tie wire and lots of carb cleaner.

 

landtoy80

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• Oct 13, 2004

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• #3

I have no CE light, thats starnge. I will ream it a good one.

 

semlin

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• Oct 13, 2004

• #4

it cannot tell. on a 94 the ECU is blind on functionality of the EGR unless the temp sensor triggers something. a blocked R port does not do that. on non-california 93's like mine and earlier there is no EGR temp sensor and no code 71.

 

landtoy80

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• Oct 13, 2004

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• #5

90 psi and carb cleaner cleaned it out.
Its all but impossabel to ream it out!

 

Lars

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• Oct 13, 2004

• #6

landtoy80 said:

90 psi and carb cleaner cleaned it out.
Its all but impossabel to ream it out!

Click to expand...

Motor run any different afterwards?

 

landtoy80

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• Oct 13, 2004

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• #7

I didn't drive it. It should only affect the EGR. If my milage drops I will plug it again.
My average this summer went from 13 to 14 mpg WOW

Does a working EGR increase or decrease mpg's?

 

RavenTai

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• Oct 13, 2004

• #8

IIRC port R is before the throttle plate when at idle so dont think it is soppose to have vacumme at idle (at least not on my 96)

someone with a loose TB could check it out, you might be able to see it sith a mirror if you removed the big hose

 

semlin

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• Oct 13, 2004

• #9

i noticed no power difference between a working and broken egr system.

port R opens your egr valve fully when you open the throttle up below 3500 rpm and the engine is hot. this increases gas recirculation (reducing NOX emissions) and potentially decreases exhaust pressure. I guess this could cost you a little power especially if you have an exhaust problem. port E is further back in the throttle body and opens the egr valve at low throttle below 3500 rpm but when only this port is exposed the egr valve will close again when you lose a certain amount of exhaust pressure and then open again when pressure builds up so the egr valve is not constantly open and not as much exhaust gas is recirculated.

 

landtoy80

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• Oct 14, 2004

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• #10

I only have vacuum on R and P when I rev the motor. But I have vacuum at the #2 PCV port on the throttle body and its in front of the throttle plate.

 

semlin

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• Oct 14, 2004

• #11

no FSM to check but I think you shoudl get low vacuum at port E on the TB when the throttle opens slightly. the pcv port is on the intake side of the TB butterfly so it is always vacuum. iirc port E and R only get vacuum when the butterfly opens with E getting it first then R. The resulting vacuum is enough to operate the vsv/egr modulator and control the egr valve as noted above. Maybe your port E is also clogged?

 

landtoy80

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• Oct 14, 2004

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• #12

I checked E and it has vacuum when its reved.

 

RavenTai

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• Oct 15, 2004

• #13

landtoy80 said:

I only have vacuum on R and P when I rev the motor. But I have vacuum at the #2 PCV port on the throttle body and its in front of the throttle plate.

Click to expand...

The vacuum is the same at those ports, the large size of the PCV #2 line just makes the mild vacuum cause by the air filter and "VAF" more apparent on the #2 port

 

landtoy80

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• Oct 22, 2004

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• #14

My first tank of gas after cleaning port R gave me 12.966 mpg.
I hope the next tank of gas doesn't go that low or I am going to plug that line again.

With port R plugged, will the EGR work at any time?

 

semlin

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• Oct 22, 2004

• #15

landtoy80 said:

With port R plugged, will the EGR work at any time?

Click to expand...

it will work the way it is supposed to until you punch the throttle at which point it will not recirculate as much exhaust gas as it is supposed to.

 

landtoy80

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• Oct 29, 2004

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• #16

My second tank of gas after opening port "R" and its now 12.48 mpg.
Could there be a relationship between port "R" and drop in mpg?

The 12 mpg was normal untill sometime this year. THen it went up to 14 mpg.
It could be that "R" slowly got plugged and my milage went up. I don't know.
I will try one more tank and then plug port "R".

 

Last edited: Oct 29, 2004