2001 Qx4 - Codes P0140,P1441,P0160,P1491

[flipdog0]

So a little background first: My 2001 Qx4 (4wd) had been running fine with no gas mileage problems however every now and then it would have an issue starting. The battery wasn't the issue and after a few tries it would usually crank right up. (what might have been causing this?) My check engine light has been on and off with the O2 censors for a while now but most recently i checked the codes and came up with:

P0140 - Bank 1 O2 sensor 2

P1441 - EVAP leak small

P0160 - Bank 2 O2 sensor 2

P1491 - VC cut/V Bypass

so fast forward, we were driving home and the car begins to shake when going high speeds (50+) then at stoplights the car wouldn't idle properly, requiring me to press the gas to keep the car running without stalling.

I havent drove it in a few months and am just getting around to attempting to fix the issue. The battery is dead but i can jump it and get the car will start but you have to hold the gas down in order to get it to run and the car smokes.

The oil is low and looks like it needs to be replaced, and i will do that first. But i have a few questions for what might be next.

Could this current problem be related to the engine codes that were showing?

What is the cheapest route to fix my issues, can the be done at home with the right tools. I wouldn't say I am particurally car savy at the moment but I would say i am able to follow directions and I am not afraid to get my hands dirty and do have the time.

If anyone has any input/insight that would be great, step by step directions or a link to similar problems would be welcomed as well.

If you need any more info and i can provide it please feel free to ask.

[zach7685]

How many miles? And Welcome!

[flipdog0]

178k, with a lot of that highway miles. I bought the car at 52k and put the rest on myself. 75% of which were highway miles

[Towncivilian]

Welcome to NICO.

Replace your gas cap with a new OEM one to begin with; this may solve your P1441 code.

Does your QX4 burn any oil?

P0140 and P0160 are both rear O2 sensor codes. Did they both pop up at the same time? If so, your ECM may require reprogramming along with replacement of both rear O2 sensors. See ITB02-002 - 2001 QX4; MIL ‘ON’ WITH REAR OXYGEN SENSOR DTC PO138-P0140 OR P0158-P0160 STORED.

[flipdog0]

Thank you both for the greetings.

I havent noticed the car burning oil in the past, but at the moment with the smoke and the low oil lever it seems as if it is burning oil.

[flipdog0]

does anyone know of any good infiniti mechanics around Castle Rock CO. Denver is not far as well as Colorado Springs.

[ncaadfinder]

Hi and Welcome!
I used to have the code P1491 come up lots as a matter of fact it seemed to be on my Service engine light for a code almost all the time. I found the problem to be when filling up with fuel, do not top up the fuel tank. After the first shut off click add no more to it. I made sure not to top up for the last 5 fills and I have never had the code come up since. I have owned it for 2 1/2 years and topped it off every time I filled it,now I don't and it worked for me. Give this a try and let us know. Good luck.

[Buzzman]

Hmmm.... Low on oil, smoking engine, rough running, need to hold your foot on the gas, shakes at higher speeds...
sounds an awful lot like it might be loose or lost power valve screws to me.????
Thoughts anyone?

[Towncivilian]

You're right, an ingested power valve screw (or multiple) can certainly cause such issues. OP, if you're mechanically inclined and feel up to the task, follow the DIY guide on applying threadlocker to the power valve screws. Hopefully you won't find this:



If you do, you've almost certainly got engine and/or catalytic converter damage as a result of screw ingestion.

[flipdog0]

So let's say I get in there and it is the screws, what kind of damage could they have caused? What type of money are we talkin both from a mechanic and DIY if it is even possible. Should I change the oil before or after te DIY guide to find the screws?

[Towncivilian]

An ingested power valve screw can cause cylinder wall scoring, damage the catalyst in the catalytic converter, and all sorts of nasty expensive things.

You don't need to change the oil either way, only the upper intake manifold needs to come off to examine the power valve screws. If you wish to apply threadlocker and change the PCV valve, you would need to remove the lower intake manifold as well.

[flipdog0]

So I i decide to take it to the dealership and or another mechanic, what types of questions should I ask them in order to avoid being ripped off if the issue is the screws and the screws didn't cause any damage. If the screws are an issue and have caused damage what would be my best plan of action and what should I look for?

Additionally, would these screws cause any of these codes I am showing?

[Towncivilian]

Ingested power valve screws should not cause any of your codes, but it certainly can cause oil burning, smoking, and poor idle.

Tell your mechanic or dealer to take a look at the power valve screws and ensure they are all there. A dealer will charge approximately $300 to check the power valve screws and apply threadlocker to them to prevent any from falling out.

[flipdog0]

So basically if all of those things are happening, chances are good I have ingested some power valve screws? And if so I could have some major damage to my engine? Is there hope that even if i have ingested a screw or two that they will be able to get the screws out and the engine is going to work? Or could it be possible that all of these things are happening and the screws are just loose?

Sorry for so many questions but I am worried about my car and I am hoping that I wont have to spend a ridiculous amount in order to get it working again.

Is there a list of reputable Nissan/Infiniti mechanics on this website?

[Towncivilian]

Either one is a possibility. If one or more were ingested, it's unlikely to know where they have ended up without a costly engine teardown.

Unfortunately, we have no such list of mechanics.

[flipdog0]

So I changed the oil today in my 2001 qx4 and it seemed as if i haven't been burning any oil. I put in 5+ quarts of oil and 5+ quarts came out. Do you guys still think the power valve screws could still be the issue? I hope to try to DIY with the help of a friend in the next few days. I will let you all know what I find.

[Towncivilian]

It's uncertain to know whether a power valve screw is a potential cause for damage until you take a look at them. Even if all are present, it's a wise idea to apply threadlocker (use red permanent threadlocker as said in the DIY guide) as a preventative measure.

[flipdog0]

Would you suggest that I buy the gaskets that are mentioned in the DIY thread? Or has it been determined that you don't need to replace these?

[Towncivilian]

Yes, buy them, you'll need to replace them.

[flipdog0]

so these are the gaskets i need to apply the threadlocker, correct? Are these only available through a Nissan/Infiniti dealer or can they be purchased at a local advanced auto/o'riellys/autozone type store?

16175-4w000 (throttle body)
14033-4w000 (right side, between upper and lower intake plenum also called 14010A*)
14033-4w010 (left side, between upper and lower intake plenum also called 14010AA*)
14033-4w00A replaces 14032-4 (between lower intake plenum and intake manifold also called 14040E*)

Are these the part numbers?

What else do i need to buy to preform this job?

the main post states to use : loc-tite 242 (blue)
but you think the red would be better? (Permatex red threadlocker?)

[Towncivilian]

Yep, those are the gaskets you need. Advance Auto and some other parts stores sells a Fel-Pro gasket kit which contain the bottom 3 (and some other one you won't need), but not a throttle body gasket so you'll need to buy that separately at the dealer or at the parts store.

Use red threadlocker, there's no need to remove the power valve screws ever again for any service so red is a wiser idea.

You will want a torque wrench to torque all bolts properly. I don't think you should need anything else that isn't common.

[flipdog0]

I still have not had the chance to take on the Threadlocker challenge. I am hoping I can get someone over here who knows a bit more about cars then me in the next week or so to attempt this task.

I did however have my friend come by and he seemed to think the engine sounded good overall, obviously the idle is an issue but I thought that was reassuring as he thought the chance of an ingested screw would be low as there was no knocking or bad noises coming from the engine. The smoke from the engine bay has seemed to taper off since I changed the Oil.... Thoughts?

I did however call Infiniti and spoke with them about potential causes of my problem. Then mentioned a potential clogged Mass Airflow sensor (on the low end of costs). And on the high end damaged or broken Idle Valve Control and/or ECM?

I procured a computer reader and plan on running the codes tomorrow to see if anything new has come up since the poor engine and idle issues arose. I will report back when I do so.

In the meantime what do you think about the Infiniti dealers opinion? The cost would be $129 for a diagnosis and then $129 an hour plus parts to fix the car. However the diagnosis charge would roll into the first hour as long as I got the work done there. I would also get a loaner car while my car was being worked on. These rates seem a bit high but at least I would be getting an experienced Infiniti mechanic which may save on labor hours?

Do dealerships allow you to buy parts elsewhere and have them install them?

[Towncivilian]

The MAF cannot get "clogged", just potentially dirty. You can clean it. Use MAF sensor cleaner spray only. Disconnect the negative battery terminal before removing the MAF sensor harness. It is secured by 2 T20 Torx screws; they may be of the security variant. Worst case, you buy a new one for $89, no big deal.

A new OEM IACV would cost around $250 shipped online. I seriously doubt you'll require remanufacture or replacement of your ECM.

Does your QX4 burn a significant amount of oil? What color is the smoke?

Don't think about the dealer just yet. Some dealers will allow your own supplied parts to be installed, naturally without warranty (unless it's a genuine OEM part).

You can attempt replacement of the rear O2 sensors yourself; the parts should not cost more than around $100 (probably somewhat less), and you'd need a 22mm oxygen sensor socket or wrench and a few hours of your time - let me know if you'd like me to link to the necessary parts. I'll need your QX4's manufacturing date if so.

Have you replaced the gas cap yet?

[flipdog0]

Where can I get the MAF sensor spray? Advanced Auto or the likes? Any particular brand?
Is there a DIY thread on cleaning/replacing the MAF sensor?

When I changed the oil It was pretty dark in color almost burnt looking (it had been sitting for 4-5 months before I got back out to the car and had been run nearly 4500 miles on that oil), but I put 5+ quarts of oil in the car and about the same amount came out.

The smoke seems white but honestly since I changed the oil I didnt notice much smoke today when we were messing with the car. It is hard for me to see however due to having to press the gas to keep an Idle.

I am not opposed to changing the O2 sensors etc. myself but If there is an issue with the Computer as far as needing to reprogram/update the software I am not sure that I can do that part. I recall taking my car to the infiniti dealer in Raleigh NC where I used to live and getting hosed for over a grand for a sensor....maybe twice. Can I get the service report on my car from them? through email? And would this be grounds for reimbursement if they didn't follow infiniti's protocols?

As far as the 22mm oxygen sensor socket or wrench, Can I find that at Advanced Auto or a similar store?

I have a new gas cap in the car and will install that tomorrow before running the codes.

I will also get the manufacturing date and VIN at that time for you.

[Towncivilian]

I would use CRC MAF Cleaner spray. It can be found at WalMart (I'm fairly sure), Advance Auto, etc. The bottom of this article has instructions.

It may not be absolutely necessary to have your ECM reprogrammed to accommodate the new rear O2 sensors - it could simply be possible that both are faulty. You should be able to ask for a complete service history printout from your local Infiniti dealer's service adviser. I'm not sure whether you can get any work reimbursed if they didn't follow a TSB when they should have. I'd need to see what work was performed to see whether it's viable to call Nissan/Infiniti's customer service line and complain.

Yes, Advance Auto, Harbor Freight, etc should have a 22mm (7/8" will also work) oxygen sensor socket.

[flipdog0]

I just went down to the car to pull the codes and I totally forgot that they reset with the battery, the car had been dead for quite some time. So I am showing no codes, which is not correct. Is there anyway I can get the car to read the codes without having to drive it?

[Towncivilian]

Starting the car and letting it idle for 5 minutes, repeating once, then restarting again might make some codes show up, but it would be easier to complete a few drive cycles since there is two-trip detection logic for most non-critical engine codes.

[flipdog0]

kind of an issue when the car doesnt want to idle no? I could potentially attempt to drive it but we are talking like 20 miles or more yea?

[Towncivilian]

Not sure, really. I would just try driving it around the block twice, with an engine restart in between.

[flipdog0]

sounds good.