PowerTotheMax

Hello, for the past 3 years I have had a p0400 egr flow code. I believe I have done everything on the fsm about that code and it always comes back. It used to come back after 1k miles of clearing it, but if i were to clear it now it will come back within 50 miles. I was able to pass emissions before when it took longer to reappear. I am also experiencing a cold engine surge (100rpms) at low speed cruising (25mph or so). After warm up it runs fine. I wonder if its related to the p0400. I even threw parts at it. Here's what I have done:

Cleaned egr tube (wasn't clogged)
Tested and replaced egr solenoid
Tested, cleaned, and replaced egr valve
Tested temp sensor
Replaced backpressure transducer (bpt)
Checked for vacuum and exhaust leaks with homemade smoke machine.

I might be missing something, but anyway I am trying to repair my 4th gen before I sell it. I bought a 5.5 gen and I don't have parking space.

If anyone has ideas that would be appreciated. Thanks.

DennisMik

iTrader: (2)

Maybe the vacuum is missing from the EGR system, like the vacuum port at the throttle body is plugged or a weak hose that collapses and closes off when it has vacuum.

See the diagram in the center of page EC-201 in the service manual.

http://boredmder.com/FSMs/Nissan/Maxima/1996/EC.pdf

JvG

I had this problem.

Dennis is right on.

Please look under the throttle body. the middle hose supplies vacuum to that whole system.

I had removed and cleaned the throttle body. I accidentally installed that middle hose so that it had a kink in it.

The kink did not long let vacuum through. I cut a little of the hose off, then reinstalled the hose without a kink.

My p400 code went away, instantly.

PowerTotheMax

Thanks. I followed both your guys advice and checked under the throttle body. There was a small diameter line with a round white saucer that looked like some sort of filter or valve. It goes mounted to the heater core hose. The end was torn but it looked recent. I was able to judt cut off then end and reinsert it. I changed the heater core hose maybe a month ago, so I probably broke that.

I also thought maybe the small hose that attaches to the nipple on top of the throttle body and the hose that attaches to the nipple on the air intake resonator were reversed. I swapped them but didnt notice any negative or positive effects. Edit: nevermind swapping was not a good idea. Swapped them back.

PowerTotheMax

Even after fixing that small hose issue and clearing the code, its back. I dont see any other cracked hoses. I read a thread about the 95 maxima including the gas cap as part of the egr code, but I have a 96. Also forgot to mention that I have a warpspeed y-pipe. Could that be my issue? The flexpipe looks ok. Im thinking since removing the cats its throwing off the egr system?

JvG

I see no relationship between your exhaust system and lack of vacuum in your ear system.

Please do a search.

others have had your problem.

PowerTotheMax

With all due respect, do you think I haven't searched in the last 3 years I have hade this code? I'm asking for help because now I am just guessing.

About your suggestion having a kinked hose, there was one that i shortened because it did look sort of kinked. That didn't help though.

And also the back pressure transducer valve relies on exhaust backpressure to activate vacuum to the egr valve. Thats what I have read. No restriction from the precats means less backpressure.

PowerTotheMax

Welp sorry to bother everyone. I'm really stubborn. Found 2 broken injector pintle caps in the front. Haven't checked the rear but pretty sure I will find more. I suppose that surge im describing is actually a misfire. It's also beginning to do that in drive at a stop light.

JoshG

yep, its either your injectors or coils. Most likely looks like your injectors as u found 2 broken pintle caps.. replace them all.. Had a misfire just like you, only at stop lights it would do it. It ended up being my coils. Replaced all 6 with new Hitachi coils back in june, still works like a charm to this day. $300 for all 6 wasn't too bad. but rebuilding all injectors is cheaper, think $120 for all 6 at a injector shop.

PowerTotheMax

I'm hoping to find some good condition injectors at the junkyard or just ordering the caps if it's even a diy job. I don't want to put that much money into the car seeing as I'm not going to get even $1000 when I sell it.

JoshG

well think of it this way, if you buy another car... chances are you either go new or used, if new.. u lose $5k within the first mile, $15k after first year(imagine what that amount could do in repairs)... another used car you could deal with their issues again and their repairs, so either way taking care of your current car is much cheaper from my experience. Take care of what you have and in the long run it will be cheaper..rather than jumping one to another to another.

don't cheap out cause I learned that the hard way... It ended up costing me more.. a little more and a bit better quality ended being cheaper. if you think about it, cheap car and that is paid off, all you have to worry is repairs.. and thats cheap, if that makes sense. Any direction you go, you are most likely not to get 100% back with any vehicle with either new or used, but thats just the way how it is.

but your choice. Good luck. Find those injectors, and see if it fixed the problem.. its either coil or injector.

PowerTotheMax

I got an 02 maxima in decent shape for $2k. I don't like having debt. Right now I don't have parking at home so I really need to sell my 4th gen. It got me where I needed and never really broke down. Just this small issue. I decided to learn manual so that's why I'm in this situation.

JoshG

so wait u sold the 4th gen and got a 02 max?

PowerTotheMax

I am trying to repair my 4th gen to sell it. Not many people want to buy a car that won't pass emissions.

JoshG

Oh I see, makes sense where ur coming from.

PowerTotheMax

I just completed the mini refurb of my injectors and what do you know; the problem was right under my nose. Somehow the intake manifold bolts worked their way loose. They were just hand tight. I suspect that's because years ago, I followed advice to just forget about reinstalling the rear manifold brackets when I did my valve cover gaskets. I didn't know my idle could be smoother. That could be partially related to the injector caps. I'm going to keep my fingers crossed that the p0400 stays away.

JvG

there is no need to spend 300 dollars on new injectors. several companies rebuild them, including ultrasonic cleaning and flow testing.

I was very happy with the service provided by injector rx in Houston. the charged labour 110 dollars. they have fast turn around time.

PowerTotheMax

Yup true. In my case all I did was replace the caps and o-rings. I bought the wrong kit so i couldnt do screens.

If I were keeping the car that's the way I would do it. Professionally is best.

JoshG

Indeed rebuilding injectors is the way to go, but good job on getting that p0400 code away. Hope it stays like that.

PowerTotheMax

Update

For anyone who is going through the same situation as me, I would just like to say that it didn't work out as expected

It passed emissions but the check engine light returned about 1k miles later. I suspect it might be some small exhaust or vac leak I am not seeing. Either way its for sale for $500 and the new owner won't need to worry about emissions for another 2 years.