01' QX4 check engine : shop can't find solution. Advice appreciated

[drob07]

Hey everyone. I love forums and I love how there is always something to learn. Thus, I am writing in hope that someone, or a collection of people, can assist me in this issue I am having with my beautifully made 2001 QX4.

I will do my best to describe this issue with you although I am not very knowledgeable with cars.

Symptoms: high/rough idlepoor gas mileage inability to accelerate at various speeds (seems to stall out and prevent me from accelerating even if i press the gas heavily) This is the big problem that I am currently facing because it makes driving a lot less safe.

Background: I have a local shop near Clemson, SC that does amazing work (protune ... please use them if you live near Clemson, located in Seneca). They are extremely knowledgeable and don't charge for things you don't need. I have used them several times with prior issues (such as replacing an o2 sensor). After an o2 sensor got replaced, the check engine light was NOT on. A few weeks down the road, the light visits me again and has not left. I dropped my car off for 2 weeks at protune to have a thorough investigation of the issue. The computer was sending lean codes which seemed to be the other o2 sensors. After those were found not to be the issue, the next potential cause was the fuel filter/pump. The filter was cleaned and the pump was replaced but to no avail. Next, they tried adjusting the Throttle position sensor and that did not cure the problem. I have heard from other sources that the mass air flow sensor could be the issue, but the shop said they tested it and found no problems. The shops recommendation, after giving it back to me with no answer and no bill , was to take it by an Infiniti dealer to have scanned and assessed. Now, we all know how that is the last resort with ANY issue regarding our car. Please provide any insight or experience that you may have with this situation. I desperately want to take care of this blessing of a car.

Dylan

[Mariach]

The only thing I could think would be either an ignition or fuel delivery problem, but seeing how you had the fuel system checked, it's gotta be somewhere in the ignition system. Check the wires/plugs/dstributer and see if its something in there

[joestrummer77]

Perform a search of this Pathy/QX4 forum for "lean code" or "stalling" or "oxygen sensor" etc......lots of threads/posts regarding this very issue. You should be able to find you answer.

I wouldn't start tossing cash for new sensors based on codes thrown after a replaced o2 sensor. From what I've read your fix is easy.

Good luck.

[joestrummer77]

"Oxygen sensor failures are a common event on these vehicles and engine. It won't destroy your engine, but you should get it replaced soon. You will probably have to replace the other side as well in the near future. They tend to fail in pairs. If this is your first time with these sensors, then you need to go to the dealer and have your computer reprogrammed (flashed) to prevent future failures. They should do this free of charge as it is a known issue. Good luck."

The above a thread regarding what sounds like it could be a prob for you.

Cheers.

[drob07]

I really appreciate the quick response. My guy at the shop did say that my next move was to take my car to a dealer. Apparently they have some technology that he did not have... maybe he was referring to this "flashing" you speak of. I would be surprised if a dealership did anything free of charge but I would certainly love it if that was true. Now that you mention it, I do remember my mechanic saying something along the lines of reprogramming my computer. I just would like to have some type of plan going into this at a dealership. I will do some research on this forum regarding those various key words. It is very possible that some other people have experienced the same issue.

Man I love forums

[mott6904]

Get the code pulled from autozone and post it up.

[Cobra99]

My first suspicion after reading the list of symptoms was going to be the mass air meter. I had the same problem. It was so bad when accelerating (surging, bucking, you name it) I really thought the transmission was the cause. I see that you said the shop tested the mass air meter and found it to be okay. My shop told me the same thing. I was fortunate enough that a friend worked at a junk yard and I was able to borrow a spare mass air to test it before having to pay for it, and that was exactly the fix. Perhaps you can borrow one from someone to try it out like that. Good luck with it either way.

[drob07]

I am actually planning on doing that exact thing hopefully within the next week. I have a friend where I live that owns the same car and year as I do. I figured it would not hurt to switch them out and run the car to test its efficiency. Did you end up getting a maxima MAF as everyone seems to be suggesting? I guess I still need to my ECU reflashed since I recently had a new o2 sensor installed. Between these two things, hopefully it will fix my car. After installing the other MAF, did your check engine light stay on or did it turn off? It would be good to have some confirmation that a different MAF is the solution.

[Cobra99]

Did you end up getting a maxima MAF as everyone seems to be suggesting?

No, it was replaced with the same model MAF out of a junkyard Pathfinder. What do people say is the advantage of using a Maxima MAF?

If I recall correctly the check engine light remained on at first, but I had it reset and it stayed off. Based on my other experiences with the light, it probably would have gone off by itself after a few days. Just last week the light came on Thursday but the car drove fine; I touched nothing and changed nothing, and it went back off Sunday.

[drob07]

I called my shop and they said that my car had sent the codes: 171 and 174.

[K03sport]

I called my shop and they said that my car had sent the codes: 171 and 174.

171 = System too lean (bank1)174 = System too lean (bank2)

According the code sheet grabbed from here. Too much air, not enough fuel. I'm guessing

The service manual is suggesting the fuel injection system.

Here are possible causes:- Intake air leaks- Heated O2 sensor 1- Injector- Exhasut gas leaks- Incorrect fuel pressure- Lack of fuel- Mass air flow sensor- incorrect PCV hose connection

[Buzzman]

No, it was replaced with the same model MAF out of a junkyard Pathfinder. What do people say is the advantage of using a Maxima MAF?

The reason is price. The Pathfinder MAF is around $400.00, while the Maxima MAF was priced below $200.00. It's the same sensor.That may have changed recently, as Nissan is catching on, but it's still worth a search. Try courtesyparts.com for starters.From the sounds of it, I think it's your MAF.

[mott6904]

both banks coming on at the same time is the mass air flow sensor. It isnt like you drive a pinto. that is probably the most expensive individual part you will put on the car.

[Cobra99]

The reason is price. The Pathfinder MAF is around $400.00, while the Maxima MAF was priced below $200.00. It's the same sensor.

That's a good reason! If it happens to me again and I can't find a perfectly functional junkyard MAF I'll definitely look to go that route.

drob, the masses have spoken. Replace that MAF and report back. I know how much it sucks driving the car like that, and I remember my overwhelming joy when I finally got it resolved.

[drob07]

It looks like I am more inclined than ever to just try someone else's MAF after speaking with the Infiniti dealer in Greenville. They are charging $96 just to do a diagnostic and that does not address the part cost either. I will give the results from the swap. I will say that the last few days my car has been running a lot better (no high idle or lack of acceleration) for no apparent reason. This whole thing seems to be a mystery. Hopefully I can switch the parts out tomorrow and get some resolutions.

[drob07]

After a long period of time, I just wanted to inform everyone who has and will read this forum about my results. As stated earlier in this post, I have had some issues with rough idling and poor acceleration. I order the Maxima mass air flow to replace my faulty one. The part only cost $80 from nissanparts.cc. Once installed, my engine light immediately disappeared I drove around for a bit and tested my cars performance. It felt so smooth and responsive. ahhh what a glorious feeling. I hope this can help anyone in a similar situation. I unfortunately stood indecisive for such a long time that I drove a poorly operating car for quite some time. Hopefully, with the help of this forum, you can make a wise decision quicker. Cheers