While this isn't a Z, it is a V6 '02 Altima so I assume the engine set up is similar. It's a 5-speed with 130K miles and when accelerating it won't make more power above around 4,000 rpm. The engine just makes more noise. It's like the engine hits a wall at that speed and in any gear. I'm thinking it might have something to do with the intake valve timing contol system. Is there a way to check this out?

 

you assume wrong my friend. totally different engines. close thread mayhaps?

 

Go to PepBoys or Advanced auto and get the car scanned to see if there are any codes. They will usually do it for free. Then you'll have a better idea of what is wrong with the car.

 

btw I was curious so i looked up your car. redlines at 6600 but peak power comes in a little over 4000 RPM so....probably isnt anything wrong thats just how the engine rolls...dawg...

 

The VQ35DE found in the 02-04, and maybe 05, Nissan Altima is basically the same long block as the non rev-up VQ35DE found in the Z. The major differences are the upper and lower oil pans, and the intake manifold forward, and the exhaust manifolds back.

OP: It's either the MAF or the VIAS. MAF failures are far more common than VIAS failure though. If the VIAS isn't working, you can do a visual check of the actual device, it should look like a rod of some sort connecting to the upper collector, if u have someone rev the engine up to around 5000rpm, you should see it moving when it engages. If it's not moving then the actuator is broken. If it moves, then its possible the butterfly assembly is broken. The butterfly assembly is fairly easy to unbolt and check if its broken or not. I'd put my money on the MAF though. I had the same symptoms on my 2000 Maxima with the VQ30DE, it ended up being the MAF. Try driving at part throttle in the same gear, let the revs climb fairly slowly, not crawling but as if you were just driving, see how the car reacts at the RPM that its having trouble at, see if it stumbles or hesitates or anything, if it does its almost definitely the MAF. Feel free to PM me.

TK

 

Try www.nissanclub.com Post there they should be able to help you. I used to there when I had my Altima SER.. give it a shot