2001 Nissan Altima 2.4L Plan of Attack

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Just had a relative move back from out of state and has a somewhat neglected 2001 Nissan Altima 2.4L with 188K miles. It generally runs just fine, but will occasionally "chug". The tailpipe has quite a bit of soot, so it appears it runs a tad rich, at least occasionally. The intake manifold gasket was replaced ~8-10 years ago. It has a 6 month old OEM alternator and main cat was replaced by an indie shop in the middle of Nevada about 1.5 years ago. Here are the codes and descriptions the scanner gave me:

P0400 EGR Flow
P0320 Cylinder 2 misfire (injector #2 measured 12 ohms)
P0420 Catalyst below threshold Bank 1 (upstream o2 sensor replaced ~2 years ago, NTK brand. Downstream o2 sensor is original)
P0440 Evap System
P1441 Evap Very Small Leak
P1126 ETC Motor Power (I've read for the 2001 model, replacing thermostat cures this, whereas the other years this pertains to throttle control. Sounds strange though.)

I've yet to get underneath it to inspect mounts and whatnot, but it has no immediately visible leaks. My plan is to address wear items first that may account for the cylinder misfire.

I will replace spark plugs (NGK plat), wires, distributor cap and rotor, thermostat, and coolant temp sensor. And, probably throw on a new gas cap for a few more dollars. I'm optimistic that this will at least take care of the cylinder misfire and hopefully, some of the others as they may be cascaded issues. I plan to then address any codes that persist after this "tune-up". The EVAP/EGR codes will probably persist, I'm fairly sure. I may pull part of the exhaust as well, to visually inspect as much of the pre-cat and main cat as I can as well as refresh the exhaust pipe gaskets/rings in case any of them are leaking and throwing off the o2 sensors.

Anyone have particular experience with this engine that could advise or add items to my plan of attack? Thanks in advance.
 
If you are getting there anyway, I personally would change out the oxygen sensors as well since the car is not running as it should.
 
When you have a bunch of codes, clear them and test drive to see what comes back first, and what doesn't come back at all.

If that misfire is real, it likely burned up the new cat. Was anything done at the time of cat replacement to fix the misfire?
 
Originally Posted By: mk378
When you have a bunch of codes, clear them and test drive to see what comes back first, and what doesn't come back at all.

If that misfire is real, it likely burned up the new cat. Was anything done at the time of cat replacement to fix the misfire?


To my knowledge, the misfire code was not present when the cat was replaced. It was replaced because the car lacked power going up mountains. Replacing the cat restored that power. I've not been able to touch or look at the car since, so I do not know when the misfire code showed up. Thanks.
 
Originally Posted By: FirstNissan
If you are getting there anyway, I personally would change out the oxygen sensors as well since the car is not running as it should.


I agree with that. I will probably get there anyways, but she is on a very limited and fixed income, so I'm trying the typical cheaper stuff first. Thanks.
 
Nissan was one of the last to adopt DBW throttles and I do recall there's a wax motor fast idle device that leaks - common problem. Are you getting insufficient EGR flow or excessive flow - excessive flow can lean out things and EVAP leaks could translate into vacuum leaks(the engine side of the EVAP system is vacuum-operated). Cleaning up the EGR valve/passages and seeing if the EGR temp sensor tests within normal parameters wouldn't be a bad idea.

Wouldn't hurt to look at an injector if there's a plug that seems sootier than the other. Nissan uses side-feed injectors, you can see if there's any flotsam that was circulating around the fuel system on the injector screen. I'd also use an OEM or equivalent thermostat, supposedly Stant has an OE-exact line that might be from the same supplier.
 
Don't forget the pcv valve, I use an oem one, air and cabin filters. Transmission drain and fill.
 
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Thanks for the suggestions everyone. I'll report back on my findings once I've had a chance to dig into a bit.......hopefully tonight.
 
I actually have that exact car with the exact engine, same model year too.

Same thing, alternator was replaced a while back, also these are notorious for leaking intake manifold gasket, mine had that replaced a long time ago too. They should have recalled it for the gasket issue to be honest, everyone had that issue, what a piece of junk.

I also had the P0320 Cylinder 2 misfire. Yes that cylinder specifically. It won't damage the cat unless the CEL blinks, if it's a steady CEL it's a problem but not cat damaging. This is per Nissan's service manual that clearly lists what the parameters are for the OBD detection logic.

Yes the exhaust on my car was sooty too. I fixed the misfire by cleaning out the EGR ports in the intake manifold. I've done a lot of work on that car so if you need help let me know. Given that you also have P0400, your problem is probably in the EGR system. If your tailpipe is that sooty, you should ask yourself what the EGR system looks like inside, chances are not better. You should do what I did, which was totally dismantle the EGR system and vacuum gallery, clean and inspect everything. I can tell you exactly what I did if you want, none of it was hard.

Also google for the service manual for that car, Nissan was helpful enough to give us troubleshooting steps for almost every single trouble code (they literally list each trouble code and steps to troubleshoot for each code specifically). A lot of the stuff in the service manual mentions their CONSULT-II scantool which I doubt you have any of their CONSULT scantools, so there's a lot of "noise" in the manual but they also give you "GST" (generic service tool/any other scantool) steps on some of them which helps.
 
Originally Posted By: NoNameJoe
I actually have that exact car with the exact engine, same model year too.

Same thing, alternator was replaced a while back, also these are notorious for leaking intake manifold gasket, mine had that replaced a long time ago too. They should have recalled it for the gasket issue to be honest, everyone had that issue, what a piece of junk.

I also had the P0320 Cylinder 2 misfire. Yes that cylinder specifically. It won't damage the cat unless the CEL blinks, if it's a steady CEL it's a problem but not cat damaging. This is per Nissan's service manual that clearly lists what the parameters are for the OBD detection logic.

Yes the exhaust on my car was sooty too. I fixed the misfire by cleaning out the EGR ports in the intake manifold. I've done a lot of work on that car so if you need help let me know. Given that you also have P0400, your problem is probably in the EGR system. If your tailpipe is that sooty, you should ask yourself what the EGR system looks like inside, chances are not better. You should do what I did, which was totally dismantle the EGR system and vacuum gallery, clean and inspect everything. I can tell you exactly what I did if you want, none of it was hard.

Also google for the service manual for that car, Nissan was helpful enough to give us troubleshooting steps for almost every single trouble code (they literally list each trouble code and steps to troubleshoot for each code specifically). A lot of the stuff in the service manual mentions their CONSULT-II scantool which I doubt you have any of their CONSULT scantools, so there's a lot of "noise" in the manual but they also give you "GST" (generic service tool/any other scantool) steps on some of them which helps.


Awesome. Thank you. Overall, this has been a very reliable and solid car. At 188K miles, some things are just worn out as almost everything is original. I have a lot of experience with other Nissans, but not so much with this one. Last night, I cleared the codes and replaced the plugs/wires/cap/rotor/thermostat/coolant temp sensor, and then took it for a 40 minute drive around town. The engine light stayed off the entire time. If it pops up again, I will definitely look into cleaning up the EGR system. I would love to see your procedure either way. If it stays off, I will move on to fluid changes/motor mounts, and then on to loose/worn suspension items.

Thanks again, everyone.
 
Well, these codes popped back up:

P0400 EGR Flow
P0420 Catalyst below threshold Bank 1
P1441 Evap Very Small Leak

NoNameJoe, I'd love to see your EGR clean out procedure! Looks like that'll be next on my to-do list.
 
First thing is get familiar with the EGR system for the Altima to know which pipes and passages connect where (credit for this goes to Nissan):
qvhjg.png

Something to note is the "collector" does not show the intake manifold, the flat/2d nature of the image doesn't reflect that the intake manifold has a EGR passage to each cylinder.

Based on that diagram there are six main things you should test:
1. The EGRC Solenoid valve. This can easily be tested using the service manual (again find this online). You pull this off the car, apply 12v to the terminals and listen for a click and also test the vacuum passage ways for continuity. There are three vacuum line hook ups on this valve that Nissan labels A, B and C and Nissan gives you a table of which passages should connect to which when the solenoid is open or closed. You can get 12v from your car, small vehicle/engine battery or even your Verizon FIOS ONT box has one, or you can just chain a bunch of 1.5v or 3v batteries in sequence to make a 12v battery).
2. The EGR valve itself. Vacuum test is easy, pull diaphragm up, plug the hole with your finger and see if diaphragm holds vacuum (or use a vacuum pump like I did). You should pull it just to make sure it's clean, clean it and inspect.
3. The EGRC-BPT valve. This is the flat/pan shaped UFO thing to the side of the EGR valve. For this one, pull it off car, blow through hose on bottom of valve, blow into it while pulling a vacuum on one of the top two hoses (plug the second hose with your hand). It should only pull a vacuum when you're blowing and release vacuum when you stop blowing. When the car is running, the exhaust gases flow through and do the same thing instead of you blowing on it.
4. The EGRC-BPT valve pipe. The hose that goes under the EGRC-BPT valve (the one you blew through) connects to a special metal exhaust pipe that is larger in diameter than rest of vacuum gallery pipes. This pipe is flared and uses a pipe fitting similar to a brake line. This pipe is wide but the actual ends have pin holes to increase pressure I assume. While not related to P0400, you should remove this and clean it up. You'll need to get a combination wrench on this and undo the fitting. When the fitting is fully unthreaded you'll need to pull toward you to pop it out, it's usually got a little rust holding it in so wiggle it. I had to remove a few bolts and nuts holding the vacuum gallery on to the intake manifold to be able to pull the vacuum gallery a little toward me to give me clearance here. Once the pipe is off, run some brake cleaner through it and a paper clip through the whole thing from both ends. You should see a lot of black liquid come out. Blow through it when done to confirm it has continuity.
5. The EGR temperature sensor. This is on the same "base" under the EGR valve. When you take this off it should be caked in carbon, clean it off and test resistance with multimeter according to service manual with a piece of ice for cold temp.
6. Vacuum lines. Check every single vacuum line that runs from the vacuum gallery to various things. These go to the fuel pressure regulator, intake manifold, air duct, the EGRC solenoid valve, EGR valve, EGRC-BPT valve. I'd just recommend replacing all of them if they're crusty and falling apart.
7. The EGR ports inside the intake manifold. If you stand on the passenger side and look at that side of the intake manifold, you should see a circle plug with a hex/allen socket. That's a 10mm hex, that plug is threaded and comes out. What I did was take that out and all of the EGR stuff off and shot a bunch of brake cleaner inside and from the top where the EGR valve mounts. A ton of black liquid ran out. Wouldn't hurt to bore brush the inside of that passage too. Be aware that you'll have to air everything out real good and there's a real possibility the cleaner might prevent the car from starting and some cleaner might end up in the cylinders and foul the spark plugs. When I did this I ran into an inability to start, fouled spark plugs, a whole mess. But I over did it on the brake cleaner and maybe should have used throttle body cleaner instead. I left everything off and left it over night, shot some compressed air through the system to air it all out and got the car working and haven't had a problem since. The first time I got the car started the fuel trims were unusually high, I just assumed that was cleaner fumes being used as fuel.

Maybe take it easier than I did, bore brush it dry first, shoot some compressed air from the EGR valve side to blow the dust out that circle plug hole, then some throttle body cleaner spraying from above and blow it out from the same side with compressed air.

Doing this cleaning fixed the misfires for good so it was worth it for me (it's been a month now, misfires never came back and it made a huge difference in how the car feels).

Some miscellaneous things:
1. This should be common sense but when you take all of the EGR stuff off, stick a coat hanger or something through the passages to make sure things connect. For example the hole the EGR temp sensor goes into should connect to the main EGR passage under the EGR valve.
2. One of the vacuum lines I would not recommend replacing is the one that goes deep down into the intake manifold. You'll know when you see it, if you try to replace this, mess it up, you probably won't be able to get your hose and fingers deep enough to put this one back on. Don't bother with it.
3. People commonly run into the hose under the EGRC-BPT valve having a hole in it. I didn't.
4. There were a lot of places where I had to use a propane torch or I would have stripped them (MAP/PRO in my case but I turned down heat so much you can just use a $25.00 propane torch). The two nuts that hold the EGR valve for example I started to round until I put heat on it, I even put a small amount of heat on the temp sensor and the EGRC-BPT valve pipe fitting. I also heated the hex plug for the EGR port on the manifold. That one I couldn't remove with a breaker bar until I heated it. I've stripped those hex plugs on Nissan's before. Be careful, don't burn any of the hoses or anything around it like harnesses (DOUBLE CHECK FOR THIS STUFF BEFORE HEATING). There's obviously a fuel rail right near this stuff too! Maybe if you're in Utah you won't have to torch it like I had to ([censored] rust).

Here's Nissan's official diagnosis chart for P0400:
shhzy.png


Here are two of my pictures when I was doing this:
fhybj.jpg

From top to bottom that's EGR valve, EGRC-BPT valve pipe (note the flared line and fitting), EGR temp sensor, EGRC-BPT valve (the hole facing the camera is the one you blow through with hose connected to that hole).

dsfwb.jpg

This is a wide shot of the EGR stuff. The orange if EGRC solenoid valve (under this on the side of the manifold is the circle plug). The blue line is the vacuum gallery under the black fuel rail wire harness. The larger red circle is the EGR valve holes, the two small ones from top to bottom are EGR temp sensor and EGRC-BPT valve pipe respectively.
 
For the EVAP system, not everyone has access to a smoke generator - my thought would be to somehow lightly pressurize the system (OEM specs no more than 1psi for testing) at the service port and listen for leaks. Are you able to fuel pump with the fuel nozzle held open or you need to refuel at a trickle - a cracked vent hose at the fill pipe may trigger EVAP codes and/or restrict fueling as the fuel dispenser nozzle needs vapor flow to function. My other thoughts besides checking the engine side(all vacuum) for vacuum leaks and a working switching valve is to check the hoses at the EVAP module for leaks and to make sure canister and solenoids/valves are working as intended.
 
Originally Posted By: nthach
For the EVAP system, not everyone has access to a smoke generator - my thought would be to somehow lightly pressurize the system (OEM specs no more than 1psi for testing) at the service port and listen for leaks. Are you able to fuel pump with the fuel nozzle held open or you need to refuel at a trickle - a cracked vent hose at the fill pipe may trigger EVAP codes and/or restrict fueling as the fuel dispenser nozzle needs vapor flow to function. My other thoughts besides checking the engine side(all vacuum) for vacuum leaks and a working switching valve is to check the hoses at the EVAP module for leaks and to make sure canister and solenoids/valves are working as intended.


Thank you. I'll check that stuff out when I'm done with the EGR stuff.
 
Here's a picture of the vacuum gallery that sits on top of the intake manifold, along with an arrow pointing to the one I recommend you not touch.
mblmg.png
 
One thing I will add, if you need to replace the hose from the EGR-BPT valve to the exhaust side of the EGR valve be sure you use high-temp hose only. Regular vacuum line will melt. My parents had a 1990s Quest with the same EGR setup and I destroyed the hose in the process of removing the intake to reseal the rear valve cover. It's a dealer or speed shop item to get high-temp line.
 
Originally Posted By: nthach
One thing I will add, if you need to replace the hose from the EGR-BPT valve to the exhaust side of the EGR valve be sure you use high-temp hose only. Regular vacuum line will melt. My parents had a 1990s Quest with the same EGR setup and I destroyed the hose in the process of removing the intake to reseal the rear valve cover. It's a dealer or speed shop item to get high-temp line.


Yep. Learned that one on a '99 Quest. Put regular hose on it. It melted.
frown.gif
 
Looks like EGR code is taken care of. Because of time constraints, I wasn't able to disassemble everything shown, but did what I could. I did find a gaping hole in that hose below the BPT. I've got the high temp hose on order from the dealer now, but have a silicone hose on there that is holding for now. The EGR code has not come back in several days of driving.

Next part to tackle is the P0420 code. My temp gun is telling me ~300-315F for both inlet and outlet temps on the pre-cat (original), so I think it's dead. I've got one on order as well as a downstream o2 sensor for good measure. Will hopefully get that switched out this weekend.
 
After replacing the pre-cat (required removal of exhaust manifold to get at a couple bolts) and downstream o2 sensor, and every vacuum hose I could find, all codes are gone except for the p1441 - small evap leak. Now in the process of tracking that down. Is probably one of the evap valve/sensors down by the charcoal canister behind the drivers side rear wheel. Will post again with what I find.

Thanks again for all the help with this!

Edit: Almost forgot. Of note, the pre-cat (original) that I removed was completely devoid of any catalyst material. It was just a hollow shell. I'm guessing those pieces accounted for the plugging of the main cat a couple years ago.
 
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