The QX4 is back and more issues to be had...

[spike753]

So the Qx4 is back from the shop after getting new cv axles and wheel bearings. This the rear end repair is also coming along after being hit the 3rd time it was driven. We have the a new lift gate and complete bumper that is being prepped for paint.

However issues still make this project the biggest pain in the a** I have ever encountered.

After a long constant drive say an hour on the freeway doing 75 or so when you shut it off and then try to re start it within 15-20 min it will give trouble trying to start. It will turn over but sputters and dies. It either sounds like its missing or not getting enough fuel. Eventually after a couple attempts and a little patience it will fire up and run like nothing was ever wrong. Since this problem is intermediate it leads me to believe it is an electrical issue vs mechanical. Most times it fires up and runs great. It is not a battery or alternator issue. It has no problems cranking over at all, (just as stated before it sounds as if it is missing or not getting fuel)

Please help,

Thanks matt

[4xq]

That might be a tough one. Do you have a scanner that can do real time data?

[spike753]

I don't believe i do for obd2. I have a obd1 usb plug and software for the camaro and ya that is super helpful as i can see live stats as i tweek things. I can see if it is in going into closed loop when it should and if things are lean or rich... Yes very handy, i will double check but i think i am out of luck on obd2. I just have a regular scanner for obd2.

I am thinking it has to be fuel or electrical related. Either the fuel pump is wearing out so after a period of long use it is almost overheated. However i am still a little unsure on the checking the fuel pressure on these 3.5s. I found a little about in the shop manual but still am unsure if there is just a standard port that i am just missing on the diagram...

Or it has to be electrical. In my past experience evertime strange issues like this occur it has almost always been a crankshaft position sensor. I have been getting some mixed results on my searching on this due to differences between the 3.3 and the3.5 that mine is. Is there just one crankshaft postion sensor?

Also another common sensor error that could cause this issue is the camshaft position sensor. I believe it is my understanding that there are 2 of these on my 3.5 engine.

Anyone have a good pic of where the crankshaft position sensor is?

[4xq]

The crankshaft position sensor is on the bottom drivers side of the engine back at the flywheel. There is a wire crossing over from the starter side of the engine to it. Can't really miss it. If it has been on the vehicle since new, when you pull it out it will have a bunch of metal filings on the magnet from the ring gear/ starter gear. (It works off the ring gear)

As far as your starting problem, the car starts in open loop always - to go closed loop coolant must be 160 degrees, oxygen sensors have to hit 600 degrees, and I think the engine must run for a minimum of 30 seconds. Then it can go closed loop.

When starting, the ecm uses its internal fuel tables and runs off the maf after it starts since it cannot yet use the O2 sensors.

There are supposed to be codes set if the crankshaft sensor or the camshaft sensor aren't reporting to the ecm in the first few seconds of cranking - you can read about that in the EC section of the manual for those sensors.

I read your first post thinking possibly fuel mixture - the ecm needs to correctly richen / lean the mixture for starting. I would want to check the coolant temp sensor and air intake temperature sensor and see what they are telling the ecm. Those sensors are not throwing codes, but they may be weak / off enough to cause hard starts with a hot engine.

You were thinking it may be an intermittent electrical issue, but the fact that the car will start after cranking for a short period kind of throws me off of that. Intermittent electrical issues aren't that "reliable" in going away - sometimes they go away quickly, sometimes it's 2 hours, and sometimes it's 2 days. You just never know. That is what steered me towards air fuel mixture.

I suppose from a maintenance standpoint I would clean the throttle body before I started doing a bunch of diagnostics just to see if it helps.

Hope that helps some -

[spike753]

Would a dirty mass air flow component be a possible cause of this issue as well then based upon your reasoning. I will certainly check the other things might be worth at least cleaning that crank sensor as well as the throttle body. I know both those sensors (crank and cam) should technically throw codes but in my past experience that has not always been the case.

Thats However that was was mainly obd1 domestic vehicles. I know these obd2 are supposed to be better about actually reporting these sort of faults. It has never thrown a code for a crank or cam sensor. However it will intermediatly throw a p0445 code frona gross evap leak. But i have checked out that system pretty throughly. When i first got the car it used to throw a p1448 as well for the evap canister value as well but since I swapped that with another I have not gotten that code sense.

Just thout that may add up i think checking the fuel pressure should be on the to do list

[4xq]

Been out getting the house ready for cold weather so I haven't posted for a couple of days. 15 degrees now. Below zero tomorrow night.

I don't really think the MAF is the cause - but it can't hurt to clean it. It's one of those sensors that doesn't always throw a code. As far as cleaning the throttle body, I just kind of begin there if there is a starting problem, no codes, and no other obvious issues. It usually results in a smoother idle. I do that to rule it out as a problem.

I kind of agree with you on crank / cam sensors, but as I think about it, I don't see many posts about those for the 3.5 engines.

And yes, I think fuel pressure might be worth checking as well.

It is hard to find these really intermittent problems when no codes are set.

[asnorton44]

[spike753]

I have been doing the same thing around here. I live just north of you in Ft Collins and sell gas powered equipment for a living so lots to winterize. Looks like we did finally got our first dose of winter. This will be the first time I try the qx4 auto 4 wheel drive system out in the snow

[spike753]

asnorton44,

Are you saying to replace these intake valve timing control solenoids? Are you thinking this will fix the starting issue or the evap code?

I am guessing the starting issue...

[4xq]

Well, I meant to ask you - when Progressive Insurance totalled me from hail damage, they said my Q (98K miles) was worth 9,000, and said residual value was 2,000 to keep it, so they paid me a net of 7,000. Was wondering what your ins. company told you when yours was hit?

Nice looking truck - I would be happy if mine looked that good.

[spike753]

The driver who hit it had geico. The car has around 160k they valved it at around 5800 and I bought it back for 550

[spike753]

I just put the bull bar on. We got it for free as the junk yard didn't charge us for it. Its a westin. I like the way it looks on it.

Did pretty well today in auto 4x4

[4xq]

Your numbers seem pretty sensible - can't turn down 550.00 bucks to buy it back! I could never have sold mine for 9k, but 7k net to me was just fine.

I have found on mine that 4wd auto does not kick in as fast as I would like. I can spin the vehicle out in a turn if I hit the gas before the front wheels kick in. (icy roads)

I pretty much lock it in 4wd high when it gets slick so I don't accidently do 360's in turns.

[spike753]

Ok so after the cold weather experience the starting problems have to be fuel/air related. During the last couple days of like -8 degrees overnight it has bought the problem to light a little more. I was hoping if it was a sensor becoming weak the cold would put enough extra strain on it to throw a code but that does not appear to be the case. So i think sensors are good. When we go to fire it up in the morning it will crank over without fuss but not be able to start. it will sputter like it is not getting enough gas to it. After 3-4 times of cranking it over and it sputtering and dying it comes to life and idles great and runs just fine. We can drive it across town say like 20 min and run into store come back out and it will fire up and run first key turn then. So what I have learned so far is in warm weather it doesn't like extended run periods of like 45 min or more where we shut it off and then try to turn it back on right away say within 10 min or so. If we run it for over 45 min and it sits all night or for a couple hours than it is fine in decent weather. In cold weather it acts like stated above.

So to me this sounds like a weak fuel pump most of all but I suppose a dirty throttle body may also play apart. When in warms up a little bit a will try to find a fuel pressure test port on it and test the pressure and clean the throttle body...


Also in the p0455 codes keeps coming up and as of this morning the p1448 code was once again back so more evap problems to be had. Those are the most annoying part of this who car...

[4xq]

Well, no Schrader valve on these to check fuel pressure. They show some kind of adapter in the FSM. You can always check it back at the fuel filter. Some cars are actually checked that way. Could be part of the problem. There are some heavier duty pumps on ebay that seem pretty well priced.

When a car has starting problems in real cold temps, I first suspect too much air / not enough fuel creating a lean condition.

I don't think the EVAP codes 455 and 1448 would cause a vacuum leak to the engine during start. Assuming the purge control valve is ok, anyway, and you don't have a code for that. But it might be worthwhile at some point to pinch off the EVAP hose at the intake manifold just as a test to see if that helps starting.

Still got the coolant temp sensor in the back of my mind. Probably because I've had problems with them before.

[spike753]

Would the cooling temp sensor effect start up though?
Like does it some how take a reading off of that on start up. I guess thats new to me.. I guess what is its function on start up?

I dont think my evap and starting issues are related thsy dont seem to correspond with on another.

I have an extra purge control valve for it and have tried (sits right on top of the engine) swapping them out with no difference to be had. I disconnected one of the hoses and got it to throw a code for that and then reconnected and the code was resolve so i believe that system checks out.

[4xq]

A cold engine starts at about a 10.5 : 1 air/fuel ratio, a hot engine runs at about 14.7 : 1. Fuel does not vaporize well at cold temperatures, so more fuel is necessary. Instead of a "choke" like on a carburetor, the ECM looks at the coolant temp sensor to determine what temp the engine is at, then uses a data table to determine how much fuel to add to the 14:7 : 1 ratio. It then holds the injectors open longer to get to the richer fuel air ratio. All done by programming. The colder the engine, the longer the injectors squirt fuel. So that temperature needs to be accurate for good cold starting.

Can't say it's the problem, just one of the possibilities. With no codes, you have to go hunting.

If your p0455 is intermittent, it could be the Evap canister vent valve sticking some times. Knock on wood - I haven't had issues with that area.

[spike753]

That makes sense and is a really good explanation. It could also explain starting issues after it has been running for some time and is already hot and not cooled down. Therefore its either making the mixture too lean or too rich. I never knew it did all that. I had figured it was more o2 sensors. I will certainly look into that once it warms up a little.

I did pull down the evap canister and looked over everything and everything seemed to check out. I actually bench tested the the vent valve with a 12 volt source and a straw to flow air to it. It checked out and worked as it should. However also thinking on the same track as you I had an extra one that I swapped it for but is still throwing the code intermittently.


I should have checked the pressure when I just replaced the fuel filter. I had just figured there was a schrader valve on it. The filter was easy enough to do so I can just pull the in hose and check it there.

Where would one find this coolant temp sensor on the qx4? There is just the one right?

a search showed TownCivilian had a great diagram from the fsm but it was for the 3.3 not the 3.5
He also mentioned that it should in theory throw a code as well if faulty.

Do you know is the Delphi the oem brand used????

[4xq]

The coolant sensor is on the coolant crossover tube on the back of the engine. You will have to pull the intake manifold to get there. So it would be better to try and see what is going on with a scanner that can do live data.

Don't know who the OEM is. Third diagram down, part 22630:

http://www.courtesyparts.com/pathfinder ... _4727.html

[spike753]

Waiting for the coolant temp sensor to come in the mail but I think I have made some progress on the p0455 gross evap leak. I have checked out the canister area well and even swapped out the valve on it to no avail. Have also checked under the hood and swapped out the purge valve with no change either. The only area that I had not checked yet was the fuel filler tube behind the left rear tire. I noticed upon walking by the gas cap area after getting out from driving it you get a strong whiff of gas from that area. Even like 2 feet away. The gas cap is brand new Nissan oem so that is good. But that would certainly explain a p0455 code gross evap leak. I understand that there is a recall on these for just that reason so I may be able to get that done for no cost.

after a week of snow driving I have to agree with you that I felt more confident locked in 4x4.

[4xq]

I noticed upon walking by the gas cap area after getting out from driving it you get a strong whiff of gas from that area. Even like 2 feet away.

Well, just crawl under there with a match - you will find the leak quickly I'm sure.

At least you are making some headway.