Comprehensive Pictures and Directons - EGR Tube Cleaning P0400
08-01-2009, 01:57 PM
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Comprehensive Pictures and Directons - EGR Tube Cleaning P0400
Hi All -- thanks for the other posts on maxima.org on EGR tube cleaning. I spent several hours cleaning mine, and decided to take comprehensive pictures. I used plywood (seen in a later picture) to put on the engine to hold my body. Enjoy!
Last edited by marktab; 07-03-2020 at 11:52 AM.
08-01-2009, 02:06 PM
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Questions and Answers
Why are you posting so many pictures and information since this topic is often on maxima.org?
The EGR Tube cleaning took me hours to finish. There is another good thread on this forum ("few pics of egr tube removal") which helped me, but it did not have enough pictures for my experience. Also, this cleaning job does not appear in my generic Nissan service manual, nor is it in the official Nissan service manual. People who repair cars a lot or who are advanced will NOT need this much detail (and there are many advanced or professional-level people on this forum). I consider this project as an intermediate-level service task, and the directions can help you or help someone you might pay to do it for you.
Do you recommend removing from the top or the bottom?
Some have had success removing the tube from the bottom (under the car). However, I believe a better solution is to remove the IACV assembly so that you can clean it. Also, the hole where the IACV assembly goes provides a way to scrape and clean the area where the EGR Tube empties into the main air flow chamber. I did NOT remove the intake manifold.
Do I need to purchase replacement gaskets?
I did not, and I made sure that I was not soaking my original gaskets with the cleaning solvent. If you do destroy yours, you could probably cut your own new ones from gasket material designed for exhaust pipes.
Did you replace your EGR flow tube?
Someone mentioned that they bought a replacement tube. I think it's sufficient to clean the tube you have unless you have some reason to get a new one (say if it rusted or cracked). Even if you buy a replacement tube, you will still need to clean the sensor off, and also the ports where the EGR tube connects to the car. I found more carbon at the top end, and I believe there was more there because of the sharp airflow angle. The IACV assembly also can be cleaned, and the IACV assembly port allows for cleaning the main airflow chamber.
How quickly can the job be completed?
We can compare how long it takes to remove the EGR tube from the vehicle. Some say they can remove it in minutes, and I believe experienced people can do it that quickly. However, the entire time is affected by how much cleaning the tube needs, and how much time you need to clean the connection port areas and the IACV assembly. In cleaning blockage, you need to at least scrape enough out to allow airflow again, and at best, you can clean these areas back to the original bare metal surface. If someone claims to do this whole job quickly, I would wonder how much time and care they put into the cleaning. Poor cleaning will shorten the time until the next required cleaning.
How often should the EGR flow tube be cleaned?
My tube was cleaned for the first time at 111K miles. It was already blocked and throwing the P0400 (same as P400) code (which is one code which will turn on the yellow engine light on the dashboard). I believe the answer varies on your oil choice, driving habits, and typical use (meaning city or highway driving). I believe that 100K is too long to wait. Now that my bottom connection nut has been hacked, cleaning it in the future will take less time.
Did the problem prevent passing emissions?
I have passed Georgia emissions every year since I got the car in 2000 (with 22K miles). This year (in January 2009), I had to replace the faulty gas cap. I do not know if this issue has been preventing people from passing emissions.
Do you recommend blowing the EGR carbon through the engine with seafoam or other solvents?
I believe that solution is NOT a good idea for this application. It is better to carefully scrape and remove the carbon deposits with fuel-injector safe carburetor cleaner. You can also spray this cleaner into the port where the IACV assembly goes. I would NOT expose my Maxima to excess oxygen or fuel, and expect it to run well, so I would NOT expect that putting extra carbon into the engine is a good idea. The carbon left by the EGR is not just black deposits on the metal wall, but thick tough carbon that I needed to carefully scrape out (mostly with a small screwdriver head).
What is the difference between cleaning the EGR flow tube and leaving it alone?
In my case, I simultaneously received the P0325 and P0400 codes together. The P0325 (or P325) code means change the knock sensor, and I was able to do that with directions from the maxima.org forum (and a replacement part from Ebay at about US$28, bought mine from the Ebay seller "abcmarts"). Changing the knock sensor alone improved my acceleration, and also improved engine starting (the engine used to require more cranking). Changing the EGR Tube has just about removed all pinging, and also improved acceleration (more). I track MPG, and have NOT seen a difference. Also, if you do NOT clean the tube, your engine will probably run (if that is your goal), but cleaning it helps restore toward the original engine performance (and probably extend engine life, even though no one could probably prove that point in all cases).
Do you believe blocking the EGR system is a good idea for Maxima fourth generation?
I do not, because of all the systems which connect into the EGR valve. You can study these connections in the official Nissan service manual (check eBay if you want to buy one). If you happen to be an automotive engineer and could prove to me comparable or superior performance using some workaround, I would like to hear about it.
Do you believe the EGR tube could be redesigned?
I believe the tube could be redesigned to allow for smoother air flow. As it is, the sensor comes into the tube at a right angle to the airflow (the sensor looks like a thermistor, a device to measure heat, and therefore a proxy for air flow). My EGR tube was most blocked at the top connection side, where the tube bends at about 90 degrees, and then goes into the main airflow chamber (and that part has a sharp bend too). None of us needs advanced automotive training to know that these sharp corners do not help airflow, and certainly not airflow filled with carbon particles. I believe a better air flow tube (and wider diameter) would be better. I have a theory that a better-designed tube would need to be cleaned less. The spacing, however, is tight, but maybe someone with good welding skills might want to fabricate and test a replacement.
So, has the light stayed off?
Yes, the light has stayed off for the last 500 miles. My story started with two engine codes, and in my case, I replaced the knock sensor first. The P0400 (same as P400) came back after less than 30 miles, and after a few weeks, I had a weekend where I decided to take on the EGR tube cleaning project.
Hopefully, this information will help you tackle the job
The EGR Tube cleaning took me hours to finish. There is another good thread on this forum ("few pics of egr tube removal") which helped me, but it did not have enough pictures for my experience. Also, this cleaning job does not appear in my generic Nissan service manual, nor is it in the official Nissan service manual. People who repair cars a lot or who are advanced will NOT need this much detail (and there are many advanced or professional-level people on this forum). I consider this project as an intermediate-level service task, and the directions can help you or help someone you might pay to do it for you.
Do you recommend removing from the top or the bottom?
Some have had success removing the tube from the bottom (under the car). However, I believe a better solution is to remove the IACV assembly so that you can clean it. Also, the hole where the IACV assembly goes provides a way to scrape and clean the area where the EGR Tube empties into the main air flow chamber. I did NOT remove the intake manifold.
Do I need to purchase replacement gaskets?
I did not, and I made sure that I was not soaking my original gaskets with the cleaning solvent. If you do destroy yours, you could probably cut your own new ones from gasket material designed for exhaust pipes.
Did you replace your EGR flow tube?
Someone mentioned that they bought a replacement tube. I think it's sufficient to clean the tube you have unless you have some reason to get a new one (say if it rusted or cracked). Even if you buy a replacement tube, you will still need to clean the sensor off, and also the ports where the EGR tube connects to the car. I found more carbon at the top end, and I believe there was more there because of the sharp airflow angle. The IACV assembly also can be cleaned, and the IACV assembly port allows for cleaning the main airflow chamber.
How quickly can the job be completed?
We can compare how long it takes to remove the EGR tube from the vehicle. Some say they can remove it in minutes, and I believe experienced people can do it that quickly. However, the entire time is affected by how much cleaning the tube needs, and how much time you need to clean the connection port areas and the IACV assembly. In cleaning blockage, you need to at least scrape enough out to allow airflow again, and at best, you can clean these areas back to the original bare metal surface. If someone claims to do this whole job quickly, I would wonder how much time and care they put into the cleaning. Poor cleaning will shorten the time until the next required cleaning.
How often should the EGR flow tube be cleaned?
My tube was cleaned for the first time at 111K miles. It was already blocked and throwing the P0400 (same as P400) code (which is one code which will turn on the yellow engine light on the dashboard). I believe the answer varies on your oil choice, driving habits, and typical use (meaning city or highway driving). I believe that 100K is too long to wait. Now that my bottom connection nut has been hacked, cleaning it in the future will take less time.
Did the problem prevent passing emissions?
I have passed Georgia emissions every year since I got the car in 2000 (with 22K miles). This year (in January 2009), I had to replace the faulty gas cap. I do not know if this issue has been preventing people from passing emissions.
Do you recommend blowing the EGR carbon through the engine with seafoam or other solvents?
I believe that solution is NOT a good idea for this application. It is better to carefully scrape and remove the carbon deposits with fuel-injector safe carburetor cleaner. You can also spray this cleaner into the port where the IACV assembly goes. I would NOT expose my Maxima to excess oxygen or fuel, and expect it to run well, so I would NOT expect that putting extra carbon into the engine is a good idea. The carbon left by the EGR is not just black deposits on the metal wall, but thick tough carbon that I needed to carefully scrape out (mostly with a small screwdriver head).
What is the difference between cleaning the EGR flow tube and leaving it alone?
In my case, I simultaneously received the P0325 and P0400 codes together. The P0325 (or P325) code means change the knock sensor, and I was able to do that with directions from the maxima.org forum (and a replacement part from Ebay at about US$28, bought mine from the Ebay seller "abcmarts"). Changing the knock sensor alone improved my acceleration, and also improved engine starting (the engine used to require more cranking). Changing the EGR Tube has just about removed all pinging, and also improved acceleration (more). I track MPG, and have NOT seen a difference. Also, if you do NOT clean the tube, your engine will probably run (if that is your goal), but cleaning it helps restore toward the original engine performance (and probably extend engine life, even though no one could probably prove that point in all cases).
Do you believe blocking the EGR system is a good idea for Maxima fourth generation?
I do not, because of all the systems which connect into the EGR valve. You can study these connections in the official Nissan service manual (check eBay if you want to buy one). If you happen to be an automotive engineer and could prove to me comparable or superior performance using some workaround, I would like to hear about it.
Do you believe the EGR tube could be redesigned?
I believe the tube could be redesigned to allow for smoother air flow. As it is, the sensor comes into the tube at a right angle to the airflow (the sensor looks like a thermistor, a device to measure heat, and therefore a proxy for air flow). My EGR tube was most blocked at the top connection side, where the tube bends at about 90 degrees, and then goes into the main airflow chamber (and that part has a sharp bend too). None of us needs advanced automotive training to know that these sharp corners do not help airflow, and certainly not airflow filled with carbon particles. I believe a better air flow tube (and wider diameter) would be better. I have a theory that a better-designed tube would need to be cleaned less. The spacing, however, is tight, but maybe someone with good welding skills might want to fabricate and test a replacement.
So, has the light stayed off?
Yes, the light has stayed off for the last 500 miles. My story started with two engine codes, and in my case, I replaced the knock sensor first. The P0400 (same as P400) came back after less than 30 miles, and after a few weeks, I had a weekend where I decided to take on the EGR tube cleaning project.
Hopefully, this information will help you tackle the job
Last edited by marktab; 08-28-2009 at 07:14 AM.
08-01-2009, 04:49 PM
#7
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Posts: 490
Good post I liked it better than whats in the sticky.
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
08-01-2009, 11:12 PM
#11
08-04-2009, 08:48 PM
#13
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Good post I liked it better than whats in the sticky.
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
08-04-2009, 08:50 PM
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08-04-2009, 09:08 PM
#15
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Thanks -- yes some of the pictures were fuzzy, but best I could do with my camera. You are correct on the orientation, but that is a general problem with following any diagrams. Once you do it once, it's easier
08-08-2009, 01:22 PM
#20
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Thanks for the feedback -- post back on how it goes. Also, if you have a recommendation on how often to clean I would like to hear it.
08-08-2009, 01:24 PM
#21
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Good question -- though even if we knew the answer, I don't know that people would typically have a choice. A way to determine the answer would be to track the results of two Maximas from this generation, one which is primarily city and other primarily highway, and see the difference over time. The importance of this question would not be in changing driving habits, but getting insight into how often the tube needs cleaning.
08-16-2009, 07:57 PM
#23
TO THE OP... EXCELLENT. YOU ARE SUPER DUPER AWESOME. I have to clean the EGR on my brothers car. and this is exactly what i needed. I saw the other post that you reffered to. BUT your pics in detail HELP a LOT.
THANK YOU THANK YOU THANK YOU
08-16-2009, 08:01 PM
#24
DE-K no EGR 
and no code from my 96 ECU with EGR.... I have the EGR flow sensor connected because it threw a code without the EGR sensor.. but once that was connected no CEL for 2 years and no clogged tube to worry about...
Now if NWP would make spacers for DEK instead of just Modding DE ones
and no code from my 96 ECU with EGR.... I have the EGR flow sensor connected because it threw a code without the EGR sensor.. but once that was connected no CEL for 2 years and no clogged tube to worry about... Now if NWP would make spacers for DEK instead of just Modding DE ones
Last edited by HomerMAC; 08-16-2009 at 08:04 PM.
08-17-2009, 11:43 AM
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Thanks for your endorsement based on your repair experience
08-27-2009, 04:11 PM
#26
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egr
hey wondering if this was all done under the car. did you replace the EGR valve also. i pushed the diaphram up on the valve and the car stumbbled does that mean its flowing right.
Last edited by mccdog; 08-27-2009 at 04:14 PM.
08-27-2009, 08:09 PM
#28
Good post I liked it better than whats in the sticky.
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
08-28-2009, 07:19 AM
#29
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I did NOT replace the EGR valve, but that issue may be important if you feel if your valve has clogged up. I have a code-reading device that I used to reset my code manually at the time I did the cleaning, so the code would not show at first. Because my code light has stayed off, I have confidence that my EGR valve is working.
I do not know the answer about pushing the EGR diaphragm.
08-28-2009, 07:34 AM
#30
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Hi Kisas -- glad to see that you may find this information useful on your Infiniti. I will give you some general idea where the area is, it's in almost the center of the engine, right by the firewall, a bit toward the driver's side. The IACV assembly is visible without removing anything, and the EGR tube is a bit behind that assembly (I do not know from memory if you can see the EGR tube without removing parts).
Because of the angles and complexity in cleaning this tube, the topic has been one of regular interest on this forum. I have rated the activity at the "intermediate" level, beyond the normal maintenance-related activities whose instructions and diagrams are almost in any repair manual. If you choose to clean your tube, maybe you can make a movie with a digital camera and post it to YouTube (I will likely do one myself, but it will likely be a few years since I have had my Maxima since 2000 and just did cleaning number one).
08-29-2009, 08:29 AM
#33
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- 12 mm combination wrench
- 14 mm combination wrench
- hacksaw blade (removed from holder)
- small screwdriver (to scrape out passages)
- channel-lock pliers (to remove hose clamps)
- phillips screwdriver (medium) -- removes one device for clearance
I think I used 3/8 inch socket equivalents at some points. Since I have rated this task at "intermediate" I would expect all these tools to be available (some may not have a hacksaw blade, but they are inexpensive and for this task you only need one blade, which will be reusable after you finish).
09-01-2009, 07:43 AM
#35
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The bottom of the EGR tube is held by two nuts, with the bolts coming out of the engine. To be completely clear, the hacking does NOT involve the nuts and does NOT require hacking a nut off. Instead, the hacking is for the excess amount of bolt on the one nut.
It would be OK to hack that one bolt to be flush with the nut. However, I did not need that much, and only hacked off what I call the flanged tip of the bolt. After the nut comes off, no more hacking needs to happen.
The following picture shows the "after", and you can compare the hacked bolt with the unhacked bolt. Because I could see both bolts with the camera, you should be able to see them with your eyes (though a small mirror may make it easier).
To answer your question, hacking this bolt makes both removal and reassembly easier. Without the hacking, the clearance between the bolt and the exhaust pipe is too small to allow the nut to slip off.
Some may believe that because of the variations on doing this EGR cleaning, that there are any number of relatively equal solutions. However, the number of possible solutions is bounded (not infinite) and there are more nonsolutions than solutions. Even among the solutions, the different solutions vary in total time and resources required. There may be more than one way to do this job, but they are provably not equal in terms of time and resources. In life, problems generally have several solutions, but under scientific measurement, possible solutions may not be equal in terms of resources or energy or work required.
09-02-2009, 06:35 AM
#36
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Good post I liked it better than whats in the sticky.
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
Wonder why Nissan produced this problem- makes you wonder if they ran any of the engines in testing past 100,000 miles b4 ok ing the egr design for production.
Ours clogged at 70,000 miles.
poor design - its burried too
Profit= None at all, Redesigning the tube and or putting in a better or newer one costs then more money then it would actually profit. Infact they would probably make a slightly higher profit then none if the parts get replaced, but probably nothing even noticeable.
09-21-2009, 10:14 AM
#38
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I too am having the issue of P0400 EGR on my 2000 GLE Max. I have followed all the suggestions posted to include the SEAFOAM treatment and replaced the EGR myself. I want to clean the Tube going into the EGR, but I can not seem to get all the bolts off. I consider myself pretty good in following pic. / dirrction. As for removing the " TUBE " what am I missing?
Please help for I am unable to pass Emmison and I am driving "DIRITY" Expired TAG. Already got a ticket #@#@!
Please help for I am unable to pass Emmison and I am driving "DIRITY" Expired TAG. Already got a ticket #@#@!
09-22-2009, 09:48 AM
#40
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I too am having the issue of P0400 EGR on my 2000 GLE Max. I have followed all the suggestions posted to include the SEAFOAM treatment and replaced the EGR myself. I want to clean the Tube going into the EGR, but I can not seem to get all the bolts off. I consider myself pretty good in following pic. / dirrction. As for removing the " TUBE " what am I missing?
Please help for I am unable to pass Emmison and I am driving "DIRITY" Expired TAG. Already got a ticket #@#@!
Please help for I am unable to pass Emmison and I am driving "DIRITY" Expired TAG. Already got a ticket #@#@!
Your car is year 2000, which makes it 5th Generation Maxima. My pictures are accurate only for 4th Generation Maximas.
You can do an "Advanced Search" and look for "EGR" only in the 5th Generation folder. To get you started, here are two links to threads on EGR tubes for 5th Generation.
http://forums.maxima.org/5th-generat...y-clogged.html
http://forums.maxima.org/5th-generat...gr-issues.html
