2001 QX4 down on power, hesition, surging, no codes.

[sporttour]

Pardon me if this topic is old but here goes. Have a 01 QX4 second owner, bought at 39k miles about a year ago, now have about 60k on the clock. Ever since we bought it it has surged under accelleration just about any rpm bout especially above 3000 rpm when trying to moderately add power without downshifting. It feels like its down about 100 horses when this happens and its happening more frequently. With the cruise set at 65 to 75 mph all is well until climing a grade then the car starts to surge and buck to the point that it downshifts and even then its feels like it is laboring to get any speed up. If you lift your accellerator foot slightly while trying to get max power it actually feels like it pulls harder, then step back in it and it just bogs...lots of intake snarl noise but no poop..! Once the rpm reaches about 4500 to 5000 rpm its finaly starts pulling with at least a little authority. It feels like it is leaning out badly and my wife says she can fhear rattling or pinging coming from the engine... I use only name brand 93 octane fuel and the best oils, the dealer replaced the MAF once and the rear 02 sensors anothe time... I have no codes and no CES lights.... fuel pressure or volume?... carbon?... I did use a K&N filter for awhile but learned my lesson... the oil may have contaminated the current MAF but I have cleaned it with the right stuff... At times when the engine is running right it really pulls hard but most of the time it fells like a dog... help please, I am tired of the dealer driving my car through the parts department.

[nissandoms47]

humm, stop using 93 octane, put in some 87 or 88 next time you fill up if your at sealevel, if your anything above that try some 85 octane. those engines dont require that octane rating. Also just unplug your battery for a couple of hours. its worth a try, but i would think running 93 octane in an N/A engine would be bad, the compression isnt that high to need the 93 octane.

[sporttour]

this is the VQ 3.5ltr. engine. It is a high compression engine (maybe more so if there is a signifigant carbon build) my owners manual recommends premium fuel and why would I reduce octane when the engine is pinging?

[Jack1944]

You could replace the fuel filter........

...and you do need to run at least 89 Octane...Mine never uses anything but 91...

[nissandoms47]

oh its a VQ.. well like what was said above, Fuel filter could cause that easily especially when you floor it. Just do all the maintance things. It could also be an ignition coil..

[Nedd]

Please post a note if you find your problem, mine is exactly the same. It's getting so bad that I can't drive my 2001 QX4 over 60 mph without it cutting out.

[sporttour]

I certainly will... after two MAFs I have my doubts about another but I was using a K&N air filter until recently.... I found a nice little pile of oily dust on the leading edge of the sensor inside the MAF.....cleaned it off and pulled out the K&N thne replaced it with a high quality no-silicone paper air filter.... the Purolator filter is the best I found next to the factroy unit... I believe there may be a fuel delivery rate problem...my fuel filter has been replaced, no change... there a many ways to restrict fuel flow both mechanically and eletcrically..... anyway I need specs.....pressure and deleivery rate from the pump to the fuel rail...... I am going to try and cut this string to the VQ engine forum, maybe there are some real Infinity/Nissan techs there.....

[nissandoms47]

also a chance that your ECU might be fried, when i was at the dealership asking about my constant SES light even after replacing the faulty sensors, they said my ecu is probably fried. they all fry different ways, but he said its pretty common on the VQ equipped r50s. so i would get that checked out. i think a diagnostics check at the dealer is like $90 bucks, at least here it is.

[C-Kwik]

You might try pulling the spark plugs. Check the gap to make sure there is no excessive wear. Also, carefully look over every plug. They can potentially give you a lot of info about what is going on inside the motor.

http://www.ngksparkplugs.com/t...2.asp

[mexgyver]

My neighbor had same problem, I put a vacuum gage on it to check Cat. Converter, it was almost completed plugged, got a new one, runs like a champ!

[infinitiwon]

My neighbor had same problem, I put a vacuum gage on it to check Cat. Converter, it was almost completed plugged, got a new one, runs like a champ!

I have same problem can u go into more detail? How do u hook vacuum hose up and where to find out if cat is plugged. And how much was it to replace cat????

[02pathy]

in terms of the vacum test try blocking the exhaust with the palm of your hand (the tail pipe). it should push your hand back with decent pressure this is in a way a cheat if there is no pressure or not alot either clogged or leaking

check spark plugs n coils, making its not running on all 6 cyclinders

put some octante booster or gas line antifreeze and give it a booth on the highway