I have a '97 Maxima V6. The Check Engine light just came on so I checked it and it seems to be a P0440 Code. There was just the one code.
How should I go about diagnosing and correcting the problem ? I did a little reading around and it seems it could come from many areas.

The car is running fine, no noticeable difference.

Thanks in advance... 97 Maxy

 

That's evap leak (large leak). You won't pass inspection with that one, have to fix it.

I've listed easier to hardest in relative.

1. check gas tank cap - it could be leaking around it. Cap is cheap. May need a new one.
2. check purge valve in engine bay. it may not be working. you have to apply 12v to it to see if it clicks (listen for sound). These are not cheap. Should check first.
3. check vacuum hose from and to the purge valve - it could have small tear - hoses are cheap - don't bother trying to get OEM, just get some universal hose if needed.
4. check purge valve next to the evap canister next to the muffler - maxima one is kind easy to look at. If 12v applied, it should click. Same, not cheap. Check first.
5. check hoses around the said canister - small tear
6. check charcoal canister- could be old or not good anymore (canister has small charcoal elements that absorb gas fume but if they get saturated by gas when over filling gas, they can sometimes get useless). You have to buy a new canister - expensive. It could also have a crack and be leaking.
7. check gas filler neck - due to rust, you can have a small hole so gas fume leaks - you can take it off from gas tank and fill it with water from one end to see if it leaks. (keep gas cap on). If small enough, you can fix it with metal epoxy. (they have one that is good with liquid and gasoline) - this happened to two of my cars. One I had to buy a new filler neck. Hole was too big to be fixed. Usually holes appear round the neck area because random overfill seeps around down and gas rusts the pipe area around the neck.
8. Hardest - check several valves on top of gas tank including fuel pump (gasket around may be leaking). You have to drop gas tank. Major pain.

Most of these you maybe able to do smoke test to see if any leaks are present. Look up for smoke machine on Youtube, lots of people making smoke machine for evap leak.
Sometimes it's very easy but sometimes it's painfully long to find where the leak is. It took me 1/2 year to find mine. I even dropped gas tank on one of the cars.

 

Thanks for your lengthy and helpful reply Glycine, it seems to have covered everything. However I'm no mechanic, maybe a weekend worrier at best. Could you or others elaborate a little further as to where these parts are located, what they look like and how to go about checking them ? Like the purge valve in engine bay, purge valve next to the evap canister, charcoal canister, ect ?
Also you mentioned applying 12v to both purge valves, how do you go about this ? Is there a +/- connector to connect to ? Does it have to be removed first ?

Thanks again...

 

You will find more information by going to you tube. Enter the name of the part, and 1995-1999 maxima.

also by googling name of part and this forum name.

all of this information is available with some research.

all the previous posts about this issue on this forum have been covered many times in the past.

We help by diagnosing a problem, then tell you where to find the information to fix it.

the you tube videos show someone actually doing the repair.

 

thanks you help me a lot you explain everything Thanks you again

 

Thanks for your reply JvG. Yes I agree, however after searching both google and YouTube I found but a few videos and articles that I thought were relevant. Quite a bit on EVAP but of different years or models and much above my knowledge as a non-mechanic. I will though look further and possibly it may eventually sink in.
Having looked under the vehicle in the last few days I see it is massively rusted. Lines running from the rear evap box are all rusted out and therefore could all be possible areas of leaks.

I was hoping that the P0440 was a more specific code that would lead to an exact area where the problem was. As have codes I've had in the past. But trying to find a leak that could be almost anywhere in a highly rusted out car is an almost impossible task. I did though check the electrical connections which all showed to have 12.x volts. I guess that's a start.

Thanks again....

 

I'm going by memory

as I recall on of the videos was about freeing up a stuck valve which is inside a long narrow plastic thing which attached to the charcoal cannister with two bolts. It has an electric connector and vacuum hoses. Mine was kinda stuck. The cleaning procedure did help.

you should investigate if there are charcoal bits in the vacuum lines. They find their way to the purge valve near the engine firewall.
If there is charcoal there, it would cost a lot of money to fix..

do you need to pass emissions inspection?

if so, you have a problem.

if not, you should be able to drive the car normally for quite a while.

 

Thanks JvG, I'll look into everything you mentioned. I do recall seeing that video about the stuck valve. Actually I saved quite a few of them on my PC.

I'll also check the vacuum lines, hopefully it's not that as I can't afford an expensive repair.
Yes, like clockwork my check light goes on every year just a few weeks before inspection is due. Believe or not this has consistently happened the last few years. I'm due in Aug, so here it is.

And yes, as you had said the vehicle still drives perfectly fine.

One question... I have an Innova 3020 code reader. I cleared the code. I tinkered around cleaned the gas cap and then out of curiosity did another reading.
I noticed the EV monitor icon was not blinking (ready) so I started the vehicle and the check engine light did not go on.
However three monitor icons ( C O E) are still blinking. Does this mean that the problem is resolved, or do I have to wait for all the monitors on the reader to stop blinking before it will show the P0440 code again ? It's also showing 0 DTC so I'm assuming there are no codes ? Or at least as of now.

Thanks...

 

I'm not familiar with your code reader.

many have an option which will let you clear the codes in the ecu and turn the cell light off.

it will come back on soon if the problem still persists.

it will also show a Not Ready status to state emission tests.

By the way. Most if us are not mechanics.

We are generally just people who have worked on our own cars as a necessary hobby for a long time.

The code you are dealing with is a bit hard to deal with for us too. It's like finding a specific suction cup on a random arm of an octopus.
The tests will help find it. But it takes a while.
Be persistant.

 

That's very true, this has to be one of the more challenging problems I've come across in all the years of working on my Maxy.
Usually the code indicates a very specific problem, though in this case it could be anywhere. And with all the rusted lines even more so.

 

You need to be methodical. Go from front to back or back to front.

- But, my suspicion is that you may have a hole in your gas filler neck because you have a large leak and you said there are a lot of rust. I would check that first because you can do it now and if it's not it then you can go through all the other nitty gritty stuff. Take down the filler neck. It's not hard- it's usually held with a few screws and bolts and take off the hose at the one end (make sure you don't have a lot of gas in the gas tank - keep some container handy so it may spill into it if too much gas in tank. Then, keep the gas cap on it then fill it with water from the other end. If you have a leak, you will see it very apparent. If a leak, you just found the hole. If too big, you can't fix it unless you know how to weld (but they are too thin metal so hard to weld). So, better to buy a new filler neck. (You do need to raise that part with a jack and use jack stand, and remove the tire).

- However, if the hole is small, you can actually use an epoxy. they have these metal combination epoxy that is also good for water and gasoline (all auto parts store sell them). I used it to fix one of our cars. It's been 4 years, no issues. It's a $6 part. Don't want to spend $60 or more if you don't have to.

Otherwise:
- I got a hand vacuum pump thing from Harbor Freight auto section (they use it for brake bleeding). Then, used it to hold vacuum at the purge valve in engine bay including the hoses.

Then, I made a 12v source from a used power supply from a junk computer PC. You can watch youtube videos on how to make a 12v power source. It's easy. PC power supply has both 12v rail and 5v rail. so, if you need a 5V power source, you can use it as well. Then, used that to check the purge valves. They all should click when power is applied. If not, that purge valve is no good. You can check the purge valve next to the charcoal canister with this as well. It cost no m

- Then check the charcoal canister - you have to drop it - near the gas tank. Either charcoal canister is no good or the hoses are torn or the purge valve is no good. As mentioned, charcoal in the canister can get all wet with gasoline when if you overfill the gas tank numerous times. It get no good. You will need a new one. Or, there is a crack in the canister and is leaking the gas fume.

- if the hoses are no good, just go buy similar hoses from part store. No reason to buy OEM stuff. Back of store has all these molded hoses you can jerry rig to fit the part. Ask them nicely and you can go there and find something that matches.

- Purge valve, you can take it off and bench check it. You can even use the car battery as 12v source to check if it works.

- If not, you need to check the gas tank. Need to drop it and check all the valves on top or any hoses connected to it. (basically is there any leaks where gas fume come out of). Need to replace that bad valve or hose that may have a leak.

Otherwise, you have a leak somewhere along the line (metal line) from engine bay to the charcoal canister. That line runs along the brake line (metal) on the car's left side bottom. That's a bad news. You will not be able to fix it (almost impossible). Hard to find the leak (need to use smoke test). You won't be able to buy the line (oem), so you have to take it apart and use some kind of metal pipe to jerry rig it. It's a major major repair.

 

Thank you for all those great tips. Yes, my concern is that it's the lines running front to back. They are all severely rusted. Just touching them they 'flack off'. But I will go ahead anyway and follow your recommendations and see. I've been watching many youtube videos on the subject so I'm getting a little more familiar with the process.

One thing you mentioned in a previous post that it was a 'large leak', is it that P0440 is indicative of a large leak ? As opposed to say another code indicating a smaller leak. I read up on P0440 but never saw anything about the actual size.

Interestingly I understand in NY they 'suspended' inspections due to the virus. So I suppose that will buy me a little more time.

Thanks again....