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Altima Nissan Altima Sedan Discussion Forum

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  #1  
Old 08-20-2007, 05:16 PM
Ion
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Default egr-bpt valve

Can anybody tell me the pressure from exaust into the [back] of the bpt valve? there is an input from solenoid and an output to egr valve, and there is the connection to the exaust, as i understood backpressure reference:how much should be this backpressure at idle and at 2000-3000 rpm?
there is pressure at input of the valve but not at the output and if i checked the bpt valve,like in the Haynes manual, looks to be ok.
ty
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Old 08-20-2007, 05:18 PM
Ion
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the car is an altima 93
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  #3  
Old 08-20-2007, 06:14 PM
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Quote:
Can anybody tell me the pressure from exaust into the [back] of the bpt valve?
Is just exhaust pressure, depends on the engine condition and speed.

With the engine turn "OFF" the air should flow freely through the BPT valve. When the engine is running, as the exhaust pressure increases the BPT valve closes. It is a very simple valve and rarely goes bad.

What is the problem with your Altima?
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  #4  
Old 08-20-2007, 08:32 PM
Ion
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Hi
I did have problems with the fuel pump couple of days ago. I replace it but for a while i thought that the problem comes from the egr system. when I checked the egr system i discovered that doesn't work at all. (and 1 month ago i passed the air care with no problems!!!)
I checked the egr valve with a vacuum pump: applying vacuum moves the membrane, ok
when engine running there is no vaccum in the hose going into the egr valve and of course ther is no signal to move the membrane. thus the problem is somewhere in the bpt valve or the solenoid
let's say that the hose coming into the bpt valve from solenoid is port 1, the hose going to egr valve is port 2 and the hose from the exhaust is port 3
When engine running there is variable vacuum on port 1 (depending on rpm) but like nothing on port 2, and i didn't feel anything coming on the hose 3. I tried to see if the port 3 is clogged, but i don't know, if I apply vacuum on that hose going to exhaust, it goes down slowly, in couple of seconds, like there is only a very small orifice in the exhaust. What pressure should i have on 3 and how should i check the bpt valve? i checked once but now i'm not sure about the procedure and the results.
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Old 08-20-2007, 09:17 PM
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Quote:
when engine running there is no vaccum in the hose going into the egr valve and of course ther is no signal to move the membrane. thus the problem is somewhere in the bpt valve or the solenoid
Is normal, the solenoid it supposed to open only when your altima is cruising at 2K-3.5K rpm.

Quote:
didn't feel anything coming on the hose 3
Normal, that is an input port. If you disconnect the hose, you should get some (very small) amount of exhaust gas coming into the valve.

Quote:
how should i check the bpt valve?
Air should flow from port 1 to port 2. If pressure is applied to port 3 there should be no flow from 1 to 2.

In 14 years working with Nissan and Infiniti and have not seen 1 bad BPT valve.
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  #6  
Old 08-20-2007, 11:25 PM
Ion
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wel, sorry about my explanations, i was not very clear
when i said there is variable pressure on port 1, coming from solenoid, but nothing on port 2, going to egr valve, that means nothing, no matter the rpm.
To test the egr system, engine must be at normal temp, and you have to increase the rpm to 2000-3000; the egr membrane should move a little. To test only the egr valve i disconected the hose and applied vacuum; the membrane moved thus the egr valve is ok.
That means on port 2 should be pressure (negative, suction) and there is not, that means on port 1 should be negative pressure, and ther it is. Now, the negative pressure on port 2 comes from the port 1, or comes from inside the egr valve? I assume it comes from port 1.
When I checked the hose on port 3, I disconected the hose from the bpt valve. I checked to see if air from exhaust is coming out but i didn't feel anything.
Also, i applied suction on the hose connected to exhaust, to see if air can flow from exhaust to bpt valve. Looks like there in the exhaust is a very little hole, while takes cople of seconds for the needle of gauge to reach 0(not instanly as i expected).
You said:" Air should flow from port 1 to port 2. If pressure is applied to port 3 there should be no flow from 1 to 2."
I understand that normally, negative pressure(suction) goes from port 1 to port 2. that means on the egr port there is always suction and the egr valve is always open. that means increasing the rpm the pressure is cut and the egr valve closes.
This is in contradiction with the egr system test, as I wrote it at the begining.
On my car there is always pressure on port 1, variable with rpm, and never pressure on port 2 no matter the rpm.
My car practically doesn't use the egr system, and while i passed the air care, and i dont feel the engine has any trouble, what is the big deal with the egr system? may cause other problem from this disfunctionality? I feel i got into a way to shut down the egr system with no troubles at all.
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