Guys need help ASAP, Engine running like crap!

[turbopugsleylx]

Hey Guys,

I am working on my friends car for him, I am a domestic kinda guy so my knowledge of these cars ins and outs is somewhat limited, though I do know alot about the different sensors and the inner workings of the car do and what can cause what, but with this I am stumped.......

My friend has a 2000 Maxima V6, here is the symptoms of the car, his car bogs horrible if you give it anything but the lightest gas, it will rarely go abovw 30 MPH or so and if it does it is a struggle getting it there.....when you press the gas down it bogs and doesnt even rev or increase in rpms, and when you let off the gas it bucks(right near the pedal level when it runs ok in the first place at ,just slight application...

Heres What we have done so far and I was hoping to shed some light on this, cause he has been to three nissan dealerships and they cannot figure it out.....

We have replaced the :

Catalytic ConverterThe PCV valvenew spark plugs, I pulled out the MAF and cleaned it with electronics cleaner and put it back inI ran Seafoam thru the vaccum system, gas tank, and crankcase to break loose and clean out any gunk in the engine comb chamber or anywhere else........considering the PCV valve had lots of carbon buildup on it.... (this product cured the problem I had very similar to this with pinging on my 94 tbird V8.

Still after all of these no change...

I need some direction on what else I can do and where the heck to start cause I am stumped

What are the symptoms of a mass air going bad?What about O2 sensors?

Any other ideas would be appreciated...

[coolhand]

Check for vaccum leaks at the base of the upper part of the intake and thottle body. Use carb cleaner to check for it. Spray around the base of the upper intake and any vaccum hoses.

[turbopugsleylx]

i am not familar with these cars u mean the black polymer looking intake part?

[audtatious]

Have you checked timing? Does he have an aftermarket intake? I doubt this is an O2 sensor problem, but the MAF is not "outta scope" as the problem.

[MinisterofDOOM]

Have you tried using a known good MAF?

[turbopugsleylx]

Well we unplugged the MAF and he said that the car did run better and had more get up to speed power but still bogged when gas applied anymore than ever so slightly, whats a good MAF, this is the stock one..

u think this could be the issue?

[MinisterofDOOM]

Well, I was just thinking that if it were my car, simply cleaning the MAF with electrical contact cleaner would not satisfy my suspicions. By known good MAF, I mean an OEM MAF that you know to be in good working order. That may (or may not) help to narrow things down. If the good MAF doesn't change anything, you know for sure it's not the MAF itself. If it does, you know that your buddy's MAF is totally shot.

[maxhopper]

I would also have my suspicions about the MAF.

Have you checked to make sure you correct fuel pressure (34 psi)?