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Discussion Starter #1
GF's 1996 Nissan 200 SX SE
1.6 liter, 5-speed, 113,000 miles

Problem:
Engine was stalling so I cleaned the TB with TB cleaner. Fixed the idle problem and all was good. Thirty-five miles later she got a CEL. Turns out to be the famous P0400 from what I've searched so far.

I removed the EGR tube and cleaned it. It wasn't clogged, but had more carbon on the TB side. Next, I applied 10in-Hg to the EGR valve while feeling the diaphragm. The diaphragm did move up and down. I thought great, that isn't stuck. Then I checked to make sure the 3/16" vacuum hose that runs to the top of the EGR valve wasn’t leaking, it wasn't. I put everything back together, warmed the car up, and held the TB open with the car running between 3000-4000 RPM and the diaphragm wouldn't budge. Makes me think I have a vacuum leak somewhere. IIRC, I couldn't move the diaphragm by hand, only by vacuum pump. Just a note, I haven't checked the EGR gas temperature sensor for resistence. I'm pretty sure there must be a vacuum leak somewhere b/c I can open the diaphragm by vacuum pump, but not with the car's natural vacuum.

Question: Just how many vacuum hoses should I check? I could only see the one on the top. Also, it doesn't look easy to remove the EGR. I ran out of time, but couldn’t see the two bolts holding it in as explained in the Haynes Manual. Hopefully, I can get it out Saturday and clean it up. I know she doesn't need the EGR system, but I don't want her to have stare at a CEL every time she is in her car. For it’s worth, I downloaded the FSM, but would rather talk to someone who has torn it apart.

-Charles-
 

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ImprezaVa said:
GF's 1996 Nissan 200 SX SE
1.6 liter, 5-speed, 113,000 miles

Problem:
Engine was stalling so I cleaned the TB with TB cleaner. Fixed the idle problem and all was good. Thirty-five miles later she got a CEL. Turns out to be the famous P0400 from what I've searched so far.

I removed the EGR tube and cleaned it. It wasn't clogged, but had more carbon on the TB side. Next, I applied 10in-Hg to the EGR valve while feeling the diaphragm. The diaphragm did move up and down. I thought great, that isn't stuck. Then I checked to make sure the 3/16" vacuum hose that runs to the top of the EGR valve wasn’t leaking, it wasn't. I put everything back together, warmed the car up, and held the TB open with the car running between 3000-4000 RPM and the diaphragm wouldn't budge. Makes me think I have a vacuum leak somewhere. IIRC, I couldn't move the diaphragm by hand, only by vacuum pump. Just a note, I haven't checked the EGR gas temperature sensor for resistence. I'm pretty sure there must be a vacuum leak somewhere b/c I can open the diaphragm by vacuum pump, but not with the car's natural vacuum.

Question: Just how many vacuum hoses should I check? I could only see the one on the top. Also, it doesn't look easy to remove the EGR. I ran out of time, but couldn’t see the two bolts holding it in as explained in the Haynes Manual. Hopefully, I can get it out Saturday and clean it up. I know she doesn't need the EGR system, but I don't want her to have stare at a CEL every time she is in her car. For it’s worth, I downloaded the FSM, but would rather talk to someone who has torn it apart.

-Charles-

Good post and troubleshooting thus far. There are 2 rubber hoses on the EGR that are prone to dry rotting, did you inspect them both carefully? Also before you go too far check the EGR temp. sensor as well. Those two items are where I would start.
 

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Then I checked to make sure the 3/16" vacuum hose that runs to the top of the EGR valve wasn’t leaking, it wasn't.
When I removed my EGR recently, there was also a vacuum hose connected to the metal tube that bolted on the bottom right part of the EGR (looking at it from the front of the engine). I have a 93 model, so I don't know if it is the same. But, if you follow that metal tube there is a vacuum hose connected to it. That one may have rotted out or could be leaking.

I removed the air intake/snorkel connected to the Throttle Body until I could rest it on top of the Throttle Body, and removed a bracket that had a wire connected to the back side of the throttle to get better access to the EGR. Not sure of your layout, but once you get better clearance, you will see the mounting bolts with good lighting. But, if it is just a bad vacuum hose, you may want to check that first before removing the EGR.
 

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There is also an EGR-BPT sensor coming off of the EGR valve check and clean it. That could be the problem. It happened to me.
 

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Discussion Starter #5
EGR hoses

First of all, thanks for all the help. I know that on a topic that has been beaten to death, questions often irritate.

I'm hoping that the vacuum hose under the EGR that connects it to the BPT is the culprit. I thought I felt around under the EGR and didn't feel any other vacuum hoses? Is this hose a PITA b/c I didn't see or feel it? Regardless, I have to fix it.

-Charles-
 

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ImprezaVa said:
First of all, thanks for all the help. I know that on a topic that has been beaten to death, questions often irritate.

I'm hoping that the vacuum hose under the EGR that connects it to the BPT is the culprit. I thought I felt around under the EGR and didn't feel any other vacuum hoses? Is this hose a PITA b/c I didn't see or feel it? Regardless, I have to fix it.

-Charles-
It can be a pain. The hose comes off of a vaccum tube of the EGR and connects under to the bottom of EGR-BPT. Mine was cracked and needed to be replaced. But I also had to clean a carbon deposit out of the nipple on the bottom of the EGR-BPT where the vaccum hose connects.
 

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Discussion Starter #7
BPT hose

While I had just a couple minutes to feel around yesterday I noticed that the hose on the bottom of the BPT was extremely mushy. Almost like stuff, or carbon build up, was in it. Maybe when I cleaned the TB all the build gathered in the EGR system?

Can I just replace this hose with the cheap stuff at the local parts store or does it need to be a specific hose with a certain heat range for the rubber and pre-bent?

-Charles-
 

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That is what I did. My hose was OK, but I unscrewed the tube from the base of the EGR when cleaning it. When I put it back, it did not line up. To give the hose some support where it needs to curve, I put a small hose clamp. Did the same thing when replacing the rotted PCV hose. Use the clamps to provide support and keep the hose from collapsing.
 

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Discussion Starter #9
Replaced the 2.5" hose running off the the bottom of the BPT, erased the ECM codes, and after a test ride everything is ok. Let's hope the CEL doesn't come back on next week.

Thanks for all the help. The Nissan guys/gals have a great resource at the hands here.

-Charles-
 
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