The infamous power loss/acceleration issue
 

When I go WOT and even slighlty less than that the car is acting very sluggish and has a dramatic decrease in power. The weird thing is its not throwing any codes and I really dont want to go to the stealership and a local auto shop called My Auto World in Kirkland believes its the MAF but wouldnt that throw a code? My only other guess would be the spark plugs or crank position sensor but then again no codes. Bad ECM maybe? I put a new drop in K&N and some people believe oily filters can cause the MAF to get dirty but that is user error from over oiling and this was a simple drop in. Any suggestions or anyone with similar issue?

unless you oiled the crap out of the filter I wouldn't think that would be the issue, first step I'd saw would pull the spark plugs and check them

Does it idle weird? When my Crank Position Sensor went, it would idle weird and stall. But never threw a code. That was on my Jeep not the Z.

could just be a cloged up fuel filter!

I would really recommend taking it to a shop that specializes in VQ's... could be something simple, could be something serious. $80/HR is a small price to pay to have the peace of mind that your car isn't going to keel over

As seymore said, likely the plugs. Have you ever changed or inspected the plugs since you've gotten the car? I just today replaced my aftermarket plugs I had put in 30k miles ago because the idle was rough and frequently misfired. While the color and wear were perfect on the old plugs, the electrodes were nearly gone. Gap measured between .066 to .077 (factory spec is .043). New plugs are in and it brought back the oompf it felt like it was missing, no idle misfires. This time I used iridium plugs so shouldn't have to replace them for a long time.

Best of luck to you and let us know what you find out.

Like everyone is saying check the spark plugs...its a possibility oil could be coming in contact with your plugs...I,m in the process of changing both valve covers I had three spark plugs drenched in oil! The Z is notorious for having faulty spark plug seals around the valve cover! Good luck

No matter what plugs you put in, you should really change them about every 30K miles if you haven't had a proper dyno tune, especially if you have some breather mods. VQ's typically run a little lean from the factory, and I can't tell you how many cars I've seen with plugs that look horrible way below Nissan's recommended 100K miles....

If you're in the Kent area swing by Intec Racing, they are very knowledgeable around VQ's and would take a look at it for no charge.

Which spark plugs you guys recommend?

NGK IX is the most technologicaly advanced high performance plug which has a 0.6mm iridium center electrode tip.
These will run you about $75/set if you find a deal but can run as much as $115/ set

Denso Iridium also is a excelent choice with a 0.7mm tip that can handle temperature in excess of 4000 degrees F.
About $13/plug

If you're going to spend that much you might as well get the greddy plugs, they have the heat range and design locked down with and exclusivity agreement with NGK, no one else can make them

Greddy's are of course great plugs but they were designed specificly for forced induction engines! Get plugs made by a company that specialisez in making spark plugs! (Cuts down on risking premature ignition)
Remember- just cuz its expensive don't mean its the best! Pick a plug that matches the power range, fuel flow and air intake of the engine! Any performane shop would be able to point you in the right dirrection! Good luck!

.... NGK manufactures the plugs for Greddy, but under a very strict exclusivity agreement. They have different heat ranges for NA and FI applications, seriously do you have any idea what you're talking about? :confused:

Nice Seymore, lets turn this into a competition for information! you win!:dunno:

:icon14:

it's lame that you have to replace the entire valve cover to fix this. my z had to have the passenger side one replaced..

I have a feeling he might not get back to you in a timely manner, his last post was in 2011. If you have aftermarket LEDs in your car, especially tail lights, might be one of the culprits. ;)