01 Qx4 falls on its face when i get on the gas

[schlaker]

I have an 01 Qx4 with 130,000 miles. When ever i get on the gas to get on the freeway, it falls on its face whenever I'm over 20% throttle. I have to back off the throttle until its at about 2000 to 2500 rpm. then it will shift, and and give me a little power as long as i don't open the throttle up too much. it's been doing this for a while, and it is rapidly getting worse. the ses light has been on. i will check codes tonight but Im sure it will give me multiple codes for o2 censors and catalytic performance.

I have a hunch that the Catalytic converters are plugged. They are still factory, and I had a similar experience with my other vehicle.
Also, when i keep it in a low gear and go full throttle, i can hear the intake sucking air, and a quick burst of a little power, then it falls flat.
I'm looking to confirm my suspicion, and find out what set of cats the problem is coming from. I am guessing that it the front, and also i would like to know if anyone has had good results from after market cats.

I have already done the thread locker to the power valve screws, even though it didn't need it. i just didn't want to send those little bastard screws thru my engine. My injectors are fine, the MAF screen is clean, i have great fuel pressure. It just feels like the exhaust is clogged.

If anyone has already gone thru this please post,
Thank you,

[Buzzman]

Getting and posting the codes should be your first step. Let us know.
Secondly, I don't think wonky O2 sensors will give you the symptoms you are describing.
Lots of guys on here, including myself, have had to replace O2 sensors, and I don't recall ever having had that problem.
I have a feeling it's the MAF.
The 2001's are prone to MAF failures. Lots of threads on that by the way, including using a replacement MAF from a Maxima (much cheaper). Try a search.
(FYI, they were different from 2002 onwards and not nearly as bad.).
Get us those codes first. Cheers.

[iceman14n]

As buzzman said, It could be the MAF.. I know that happenes but depending on how the RPM is behaving, it could be the fuel filter because i remember i only had 10 L of gas left in my tank in the other day, and i was assending up a hilly road and my gas kept getting cut because (duh... the gas wasnt being supplied) and as soon as i would go downhill, NO PROBLEM... so you might be having the fuel issue.

Tell the codes...

[chicoson]

my 01 did the same when my MAFS went bad. it didnt throw any codes and it would be fine cruising but it would kind of sputter and surge when i would give it part throttle. got a new MAFS off ebay for 55 shipped and no issue since. simple fix. maybe borrow a friends to try and diagnose it (if you have friends with a 3.5 pathy or QX or any VQ35 for that matter)

VERY IMPORTANT NOTE: NEVER CLEAN A NISSAN MAFS WITH ANY TYPE OF CLEANER. thats how i broke mine lol.

[Towncivilian]

I've cleaned my 2001.5's original OEM MAF with some CRC Mass Air Flow cleaner, and had no issues.

You can get an OEM Maxima MAF for around $89 if you feel that you should replace the MAF.

[schlaker]

Thanks guys, It is so bad that i couldn't even get it up to 30 mph. If it is the MAF i'll be relieved.

[schlaker]

It was the MAF! I'm pretty relieved about it too. I also replaced the fuel filter, and it is like driving a new vehicle again. Thank for the tip fellas.

[Towncivilian]

Great to hear it! What MAF did you obtain to replace it? $89 Maxima MAF, or something else?