Slartibartfast Posted January 22, 2014 Share Posted January 22, 2014 There was clearly something wrong with your old motor, but the EGR is the last place I'd look. The EGRC solenoid is controlled entirely by the computer, so I don't imagine it requires vacuum. It's also the only component of the EGR to which the computer is connected (so far as I can tell), so a fault with it is likely causing your code. I would unplug it and probe the connector with an ohmmeter (or hook it to with power to and listen for a click). If the circuit inside is broken, the computer can't work the valve, and I imagine that's about the only thing that could make it throw an EGR code. If the solenoid is fine, check on the plug and the wiring around it. If I'm reading the manual correctly, a dead EGRC solenoid would mean that the EGR was on all the time (no cut off at high or low RPM), which might decrease peak power a little and make it idle poorly, but I don't see how it would cause knocking. I'd sort out the EGR code, reset the computer, then see if the knock code returns. If it does, you have another issue. Link to comment Share on other sites More sharing options...
peejay Posted January 22, 2014 Share Posted January 22, 2014 Thanks for the response Slartibartfast! I think the FSM has it wrong here, again... On page "EF & EC-16", it says of the EGR Control (EGRC)-Solenoid Valve, "The EGR system is controlled only by the ECM. At both low- and high-speed revolutions of engine, the solenoid valve turns on and accordingly the EGR valve cuts the exhaust gas leading to the intake manifold." And on page "EF & EC-21", it says "...When the ECM detects any of the following conditions, current flows through the solenoid valve in the EGR control vacuum line. This causes the port vacuum to be discharged into the atmosphere so that the EGR valve remains closed. 1) Low engine coolant temperature 2) Engine starting 3) High-speed engine operation 4) Engine idling 5) Excessively high engine coolant temperature 6) CPU malfunction of ECM and camshaft position sensor malfunction" However, the diagnostic/test procedure indicates that the EGRC solenoid is "normall" closed/off, and becomes energized under certain conditions (engine speed at/above 2,000 RPM, wheels in motion)...and the FSM tests would indicate that the EGRC solenoid actually OPENS when energized (by the ECM) to allow vacuum to flow through the solenoid and to the EGR valve, to OPEN the EGR valve, allowing exhaust gas to enter the intake...so instead of the system cutting exhaust gas when activated, it seems like it admits exhaust gas when activated... I still don't get what the port "C" is for...why does the solenoid need two inputs (port A & port C)? Why am I not seeing vacuum at the hose that connects to the intake boot? Link to comment Share on other sites More sharing options...
Slartibartfast Posted January 25, 2014 Share Posted January 25, 2014 I had a look at mine, did some reading, and then spent far too long thinking about it. This is what I've come up with. Port A off the EGRC solenoid goes to the middle of the intake hose. It's not intended to be a vacuum source. Vacuum is created by a restriction and a sucking force. The engine's a sucking force, but the only significant restriction before that point is the airbox. Unless your filter is badly clogged, you shouldn't see much vacuum here. Port B off the EGRC goes to the EGR valve. The EGR valve opens with vacuum and closes without. It's a little more complex if you have a BPT valve (brings exhaust pressure into the equation), but you don't, so let's stay out of that. Port C goes under the intake hose and then hooks into the throttle body. The throttle body exists to restrict air flow, so unless it's wide open, it'll pull a vacuum. So why the two inputs? The EGRC is a three-way valve--not a valve like a thermostat that allows flow or doesn't. (If you're familiar with electrical relays, think of it as having an normally open, a normally closed, and one common.) It hooks port B to either port A or port C. With the power off, it connects port B to port C, allowing throttle body vacuum to suck the air out of the EGR diaphragm, opening the EGR valve. With the power on, the EGRC connects port A to port B. Air from the intake is drawn into the EGR diaphragm, vacuum is lost, and the EGR valve closes. If the EGRC simply closed off port B, vacuum would remain in the line, and the valve would remain open. That's why port A is necessary. It's a source of air to fill the vacuum that the throttle body created. That's all it needs to be. I suspect it's only connected to the intake because 1) the air is filtered (remember it does end up going into the engine) and 2) it's right next to it anyway. Hopefully that clears it up a little. Link to comment Share on other sites More sharing options...
peejay Posted January 25, 2014 Share Posted January 25, 2014 Slarti, Thanks for the response! The part about "...vacuum would remain in the line, and the valve would remain open..." reallys clears up why there is an "A" and a "C"! I have but "one last question"...according to the FSM, the EGRC solenoid should receive a ground signal from the computer at 2,000 rpm, and that vacuum should exist at the hose leading to the EGR valve ("B")...this leads me to believe the computer is calling for EGR at 2,000 rpm, which means the EGRC solenoid is allowing vacuum to lift the EGR valve at this rpm? And that under 2,000 rpm (or at high RPM), the computer does not send a ground signal to the EGRC, so that the solenoid does not admit vacuum to the EGR valve? I tested this on my engine, with the voltmeter connected to ECM terminal 104 (for EGRC), battery voltage starts appearing at 2,000 rpm, and returns to near zero at idle... is something wrong with my EGRC solenoid? or is my ECM sending a ground signal at the wrong time? That is, it should be sending the ground signal at rpms of less than 2,000 or greater than, say, 4000? Link to comment Share on other sites More sharing options...
Slartibartfast Posted January 26, 2014 Share Posted January 26, 2014 That one took me a minute... but I think I've got it. The manual says the ECU supplies ground to the sensor, but what you're seeing (and what's indicated in the testing procedure above) is voltage to ground. Which means that the pin coming out of the ECU is - when the EGRC is engaged. Ground on your vehicle (as on most vehicles) is also -. If we assume that the EGRC has a + and a - wire, and that the - one is switched by the ECU, that means the + side is likely unswitched--wired straight to + through the fuse links or something. So when the ECU wants to engage the EGRC, it connects the EGRC control pin to ground. But there's a weird bit (if my assumptions are correct). When it's not connected to ground, the pin shows up as positive. The ECU can't turn the pin 'off,' it can only switch it between + and - (kind of like how the EGRC switches between A and C). I'm not sure if this is by design or just a side effect of the power transistor configuration the ECU uses, but I'm fairly sure it's what you're seeing on the voltmeter. I saw something similar when I rewired my cargo area dome light to the tire carrier switch (the stock switch was worn out). It turned on like I wanted it to but with the ignition off, the carrier shut, and the dome light set to 'auto,' the tire carrier warning light on the dashboard would illuminate. It turned off when I turned the ignition on. This made no sense to me. It turned out that the voltage regulator in the dashboard (which is a + connection when the ignition is on) was somehow acting like a ground, making a circuit between itself and the unswitched + line going to the cargo light. I stopped the regulator from supplying ground (hacked a diode into the wire) and the warning light went back to normal. So when you see battery voltage, that means that the EGRC wire coming out of the computer is not at ground--and it has to be at ground for the solenoid to open. Both wires to the solenoid are positive, so nothing happens. When that pin switches to negative, you have a circuit, and the EGRC solenoid becomes energized. But your voltage tester, hooked between that pin and ground, shows no voltage until the pin goes positive again. As to why Nissan wired it like this... I have no idea. It seems to work, though. Anyway, it appears that your ECU is functioning properly. Now that it's ruled out, I'd check on the EGRC itself. Probably easiest to just unplug it, run power to it with gator clip test leads, and listen for a click when you connect it (engine off of course). If it doesn't click, it's your problem. If it does, check out the electrical plug and the wiring around it. Also, looking through the manual again, I see that there's a temperature sensor for the EGR as well, which I didn't notice when I took a look at mine yesterday. If the EGRC tests fine, you might try and track this temp sensor down and see how it's doing; since it's part of the same system, I suspect a fault with it would show the same code. Link to comment Share on other sites More sharing options...
peejay Posted January 27, 2014 Share Posted January 27, 2014 Slart... you...are...the...man! didn't know a circuit can be switched to behave as positive or negative! (but I still got the CEL, might need to PM you if that's ok!) Link to comment Share on other sites More sharing options...
Slartibartfast Posted January 28, 2014 Share Posted January 28, 2014 LOL thanks. PM me if you want, I can't guarantee anything (I don't have much experience troubleshooting) but I take this kind of thing as a challenge. This thread just showed up in the "Similar Topics" box below; check out Adamzan's post at the end of it about having a split hose throw the EGR code. If the vac hose was split, it wouldn't hold vacuum, so the EGR valve wouldn't open. The EGR valve probably runs pretty hot when it's open (hot exhaust gas and all), and cools significantly when it's shut. This means that by monitoring that EGR temp sensor, the ECU could check up on the EGR operation, compare it to an expected value, determine that the EGR wasn't functioning, and throw this code that you're dealing with. Given the age of these things, checking the condition of your vacuum lines makes sense anyway. If you find dry rot/cracks, you might have a really easy fix on your hands. Actually, it might be an easy fix to both codes: If you've got a bad vacuum leak, the engine will run lean, and a lean mix can cause knocking. Link to comment Share on other sites More sharing options...
peejay Posted January 30, 2014 Share Posted January 30, 2014 Thanks, Slart... I'm waiting to thaw out from the "Snowmageddon" (ice) here in Atlanta...I should be able to re-run the tests for EGR Function as outlined in the FSM, then I'll report back to you. Having a PROPER understanding of how that solenoid works this time should help me out, I hope it's as simple as a clogged EGR valve, but I need to make sure I'm getting vacuum to the valve, when it's supposed to! (i replaced the 3 EGR vacuum lines not too long ago, one was suspect, and just did the others off GP!) Link to comment Share on other sites More sharing options...
tmoore4512 Posted August 24, 2014 Author Share Posted August 24, 2014 Going 4.3 simply because its 100 times cheaper to build, will create more power, and the parts are way easier to source than the VG30... No argument about the strength of a VG30 built or not... I am a believer, but for my budget it is cheaper to do a complete drive line swap then to rebuild the tired VG30. I would hate to spend the money on building the VG, then have the transmission go belly up... So I saw that I said the above...and guess what...my trans went belly up...and so did the rebuilt trans I swapped in...but hey, my old VG30 is still running...going to get an Xterra trans in the morning... Link to comment Share on other sites More sharing options...
Manik Posted August 25, 2014 Share Posted August 25, 2014 It didnt surprisingly enough! It was just giving the code that there was an EGR malfunction, I'm assuming with this, its not enough to throw it into 'limp mode'. It was getting the reading off of the the egr solonoid valve which has been yanked as well. The EGR is more or less for exhaust emissions and we don't have them on Vancouver Island. I'd still have it on of I hadn't cracked the egr casing itself trying to undo the exhaust tube. (damn manifold stud replacement). The only other thing I noticed since doing this is that the exhaust smells a bit 'richer'. Overall, I wouldnt recommend taking it out if there's no need to but if it is and you live somewhere there's no emissions laws, it doesnt hurt anything. Maybe just a bit of a drop in power but hey, on the pavement, these things are about as 'performance' like as a deep freeze on tires. Ok, the purpose for an EGR valve is strictly for emmisions, it scavenges from the exhaust and routes the spent gasses back into the combustion chamber to lower emmisions at high speed. Usually above 30 mph, if you wanna call that high speed. The EGR control valve is opened up by the ECU at speed with just the purpose of lowering the amount of fuel being burned and lowering emmisions in the process. It should have little to no affect on mileage, but, could gain power on the top end because the engine is actually burning a cumbustion chamber full of fuel and not fuel and spent gasses. The EGR has absolutely zero to do with starting of the vehicle due to its function as a piece of emmisions equipment. The piping under the upper plenum that the coolant runs through serves to warm the air coming into the throttle body on cold starts, which helps with drive ability and low speed emmisions. I've also thought about doing an EGR delete on my 95, but, to deal with the CEL, I'd leave the EGR control solenoid connect so the ECU thinks it has a working EGR. The older OBD1systems do not have a way for the ECU to check EGR function, that came later with the OBD2 systems and fully electronic EGR valves. Hope this clears some things up. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
pathykline92 Posted August 31, 2014 Share Posted August 31, 2014 Ok, the purpose for an EGR valve is strictly for emmisions, it scavenges from the exhaust and routes the spent gasses back into the combustion chamber to lower emmisions at high speed. Usually above 30 mph, if you wanna call that high speed. The EGR control valve is opened up by the ECU at speed with just the purpose of lowering the amount of fuel being burned and lowering emmisions in the process. It should have little to no affect on mileage, but, could gain power on the top end because the engine is actually burning a cumbustion chamber full of fuel and not fuel and spent gasses. The EGR has absolutely zero to do with starting of the vehicle due to its function as a piece of emmisions equipment. The piping under the upper plenum that the coolant runs through serves to warm the air coming into the throttle body on cold starts, which helps with drive ability and low speed emmisions. I've also thought about doing an EGR delete on my 95, but, to deal with the CEL, I'd leave the EGR control solenoid connect so the ECU thinks it has a working EGR. The older OBD1systems do not have a way for the ECU to check EGR function, that came later with the OBD2 systems and fully electronic EGR valves. Hope this clears some things up. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
pathykline92 Posted August 31, 2014 Share Posted August 31, 2014 I just finished installing my 95 vg30e into my recently purchased 92 pathy. My 95 didn't have the egr valve like the 92 did. Should I be using the ecm from the 95. Not sure if it matters, truck seems to run fine so far. Only the first week on the road though. Link to comment Share on other sites More sharing options...
Nefarious Posted August 31, 2014 Share Posted August 31, 2014 95 ecu has more refined fuel and timing maps, so you may get a little better efficiency (slight). Other than that if it works it's fine Link to comment Share on other sites More sharing options...
Alkorahil Posted September 4, 2014 Share Posted September 4, 2014 I will say this. The last year of the VG30e in the D21U Hardbody had the EGR deleted after production date 01/95. There is even a Nissan TSB about this. Nissan states in the TSB that the EGR was not needed. NISSAN D21 1995 Technical Bulletin #FC0010095 NISSAN D21 1995 technical service bulletin was issued Jan 01, 1995. NISSAN D21 1995 EGR ELIMINATED ON VEHICLES WITH VG30 ENGINE. That being said, it is considered by the Federal Govt to be very naughty to modify the emissions on a vehicle. Link to comment Share on other sites More sharing options...
Nefarious Posted September 4, 2014 Share Posted September 4, 2014 I noticed no difference in how my truck ran with or without the egr to be honest. I know most jdm nissan don't even have egr at all. I ran without for a year and had no issues. Link to comment Share on other sites More sharing options...
Cuong Nguyen Posted April 9, 2016 Share Posted April 9, 2016 Tempted to remove my EGR setup or add a BPT. I'll decide when I get around to building a new exhaust setup. Link to comment Share on other sites More sharing options...
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