MY1PATH Posted January 5, 2012 Share Posted January 5, 2012 Hey guys, my curiosity peaked enough finally to ask this. On some of the MPFI pathfinders there are two EGR valves attached to the manifold. one on top of the other. I think it may only be the ones with Manual transmission. I'd like to know why this is or if anyone has any incite to the matter. That being said I know EGR does and I know that there are many opinions about EGR (and emissions in general) and whether or not to keep them etc... Leave all that at the door please and focus on the question. Link to comment Share on other sites More sharing options...
Tungsten Posted January 5, 2012 Share Posted January 5, 2012 (edited) It's a BPT valve. http://www.nissanpathfinders.net/forum/index.php?showtopic=30704&view=findpost&p=582631 The BPT valve uses the exhaust back pressure to modify (or reduce) how much vacuum the EGR valve receives, which determines how much the EGR valve opens. So in a case where there is too much back pressure built up, for example during a high load situation, the BPT valve releases the vacuum to the EGR valve to close or reduce the EGR valve to gain more power. In other words, the BPT valve is there to create a vacuum leak, which is why it should have a filter, to disable the EGR valve for more power. If the BPT valve does not operate properly, for example if the diaphragm is torn or the valve is damaged, it is like having a vacuum leak to the EGR valve, which will cause the EGR valve to never open resulting in no EGR operation. On the contrary, if the BPT valve never opens, from less back pressure for example, it's like the valve does not exist. The BPT valve can be bypassed by disconnecting the small vacuum hose that's on it and plugging it; this is the hose that goes from it to the EGR valve and the override solenoid. Then the EGR valve will be controlled only by the intake manifold vacuum and the override solenoid but I have no idea if that may cause issues at certain speeds and/or loads. To test the EGR operation, connect a vacuum gauge to the "vacuum signal source" and see how much vacuum there is. If there is at least some vacuum then the EGR is operational and if there isn't any then the EGR system is non-functional. Edited January 6, 2012 by Tungsten Link to comment Share on other sites More sharing options...
silverton Posted January 6, 2012 Share Posted January 6, 2012 Garret, just FYI, EGR is not needed to pass emissions in Washington state. Link to comment Share on other sites More sharing options...
1994SEV6 Posted January 6, 2012 Share Posted January 6, 2012 Wow. That's all pretty interesting. Boy, the systems and contraptions that people come up with... Tungsten, I don't know if you wrote that personally, but great explanation. Does anyone know the system to which vehicles had it? I was looking at pictures on the thread that Tungsten linked and I don't have that device with the vacuum hoses. Link to comment Share on other sites More sharing options...
Tungsten Posted January 6, 2012 Share Posted January 6, 2012 I did write that, I reverse engineered that entire system. The BPT valve only came on late 1995 VG engines, on California models, and on some Canadian models. You can add that system to your truck if you don't have it and there is a good increase in performance with it. Kind of like cutting off the EGR but at the same time still keeping everything state inspection legal. 2 Link to comment Share on other sites More sharing options...
5523Pathfinder Posted January 10, 2012 Share Posted January 10, 2012 (edited) From the 94 manual... Exhaust Gas Recirculation (EGR) Valve The EGR valve controls the quantity of exhaust gas to be led to the intake manifold through vertical movement of the taper vavle connected to the diaphram, to which vacuum is applied in response to the opening of the throttle valve. EGR Control (EGRC0-BPT Valve The EGRC-BPT valve monitors exhaust pressure to activate the diaphram, controlling throttle body vacuum applied to the EGR valve. In other words, recirculated exhaust gas is controlled in response to positioning the EGR valve or to engine operation. Edited January 10, 2012 by 5523Pathfinder Link to comment Share on other sites More sharing options...
Tungsten Posted January 10, 2012 Share Posted January 10, 2012 The service manual is a lie. The BPT valve doesn't monitor the exhaust pressure, it is directly affected by the exhaust pressure. The more pressure the BPT receives from the bottom, the more of a vacuum leak to the EGR valve it creates. It is that simple. Link to comment Share on other sites More sharing options...
5523Pathfinder Posted January 10, 2012 Share Posted January 10, 2012 (edited) It doesnt create a vacuum leak, it uses backpressure to open the EGR during cruise when backpressure is at optimal(not under load). This allows exhaust gasses to be recirculated to reduce emission, specifically NOX. Edited January 10, 2012 by 5523Pathfinder Link to comment Share on other sites More sharing options...
mfoley412 Posted October 24, 2014 Share Posted October 24, 2014 I have experimented with taking my bpt valve off because my pathfinder throws an egr code, but with the bpt valve off and lines plugged the code goes away, not really sure if I notice a difference in performance but it is nice to not have to look at the check engine light. Anyone else have this kind of issue?? and is there a way to test if the bpt vavle is working correctly, I kind of just want to get rid of it for good I hate seeing that light on the dash! Link to comment Share on other sites More sharing options...
5523Pathfinder Posted October 24, 2014 Share Posted October 24, 2014 (edited) Page EF & EC-135.... http://www.nicoclub.com/FSM/Pathfinder/1995_Pathfinder/ec.pdf#page21 Edited October 24, 2014 by 5523Pathfinder 1 Link to comment Share on other sites More sharing options...
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