Just as an FYI (I know the original poster has solved his issue), I was having a very similar issue the past few days. Mine was lagging around 3 grand or so. Tightening down the plenum's bolts did end up resolving the issue thus far.

I believe we used 7 foot lbs of torque (84 inch lbs) to tighten the bolts, just in case it helps anybody else out in this situation.

Now.. to fix that damned clutch pedal issue...

 

vacuum leak. 7-8 ft lbs is all you want them. Use some blue loctite if you want to ensure they stay good.

 

Suck out all the clutch fluid with a syringe and replace it with some valvoline dot 4 brake fluid drive for a while and then drain it again. then replace every couple months.

 

^^ +1111

This is how I did it -

1. Suck fluid out with turkey baster as low as you can, fill back up with dot4.

2. Pump clutch 20 times

Repeat...

I did it as many times as it took until the fluid I was sucking out was perfectly clear. Took 5 times the first time I did it. Clutch is like brand new again. This resolved both sticking and roughness.

Worked for several other people I told this to as well.

 

yup.

 

Well I'm back to square one. The problem returned shortly after the bolt tightening on the plenum, so I went ahead and took the thing apart, reseated it and still problem was there. I even tried gray RTV sealant with no luck, then even removed the pwoerlab spacers gaskets and used 2 original metal plenum gaskets with exactly the same results. Tonight I just removed teh spacer altogether essentially bringing the plenum to stock and the problem is still there. So I can damn well safely say its not a vacum leak at the plenum. At this point I think i might just order the osiris cypher and try to diagnose the problem with the software unless someone here has suggestions for things to try. Any ideas ???

 

are you running test pipes? because I am having the same problem. After fixing the plenum. I found that my flex joint in my MR test pipe blew out. This was caused by too much flow to the rear muffler and collapsed some baffles that are clogged the output. It has cause my ecu u to f up like crazy and I have the osris tune. So to fix this Ih the short term i am ordering an XO2 exhaust to replace it all. this should fix it.

 

nope, no test pipes :/

There are two things I'm suspecting at this point. Either fuel pump or throttle body. I know what the usual symptoms of a bad throttle body are so thas my second guess. Does anyone kno what the symptoms of a bad fuel pump or a pump thats starting to show signs of wear ?

 

Row2k- Is you problem noticeable in 1-3rd gear too? I notice a lag at 5th and 6th gear too, but its most noticeable at 1st-3rd. The most noticeable thing is after up to full temp running for 10-20 mins is that if I turn the AC on, and try to take off in 1st, there is a 2 sec lag where there is no response at all, then it slowly goes through the revs.

When I run the car right at or slightly before full temp its prefectly time, I can break traction at will and am pinned to my seat, but after up to temp, its like driving a Kia.

I am getting SOOO tired of this, I'm about ready to sell this thing and get a E46 M3 and open up a whole new can of worms, haha. A friend of mine that works at an import shop that works on G35/350Z's primarily seems to think this has to do with the MAF or something electrical. Either way I just want it fixed!!!

 

Yup, that sounds about right. Its mostly noticeable in the higher gears and especially under load at lower rpms. In example if im in 6th gear and stomp on it around 2000rpm I am pretty much guaranteed that the car will shudder and just "choke" and then very slowly start gaining speed, but no where close to normal acceleration. Bear in mind this is only after about 15 to 20 min of warming up. I will solve this if its the last thing I do, I am way too fakin determined to give up on this, its just a matter of time and troubleshooting. At this point I am leaning towards the osiris cypher and just running logs to see whats out of normal.

 

What codes (if any) are you throwing? Sounds like a bad MAF or cam sensor.

 

I have no codes being thrown, thats what has me sooo dumbfounded. My buddy that works in an import shop also thinks it could be a MAF sensor. I tried cleaning mine out with some electronics cleaner, but if its bad its bad. Is it possible for it to go bad and not through a code? I guess if it just thinks the air quality is too hot it would just retard the timing and not throw a code? I'm taking mine to a buddy of mine that owns APR Audi shop, his head tech is real good with JDM cars and is one of the more intelligent car guys I've met, so hopefully he can figure out what I can't.

 

I have absolutely no codes either and that makes this problem that much more difficult to diagnose. I went ahead and ordered my walbro GSS342 fuel pump, perhaps this solves the problem and if not at least its one less thing i'll have to buy when i go FI . I'm prob also going to try and pull the maf sensor again, does anyone know if an 07 murano uses the same MAF as our cars? I could just swap it for a day from my moms car if it does.

EDIT: Just checked the MAF sensor part numbers and an 03-08 G35 and and 03-07 Murano use the same MAF sensor, so tomorrow I'll get to eliminate one more potential cause of the problem.

 

Homie, did you end up throwing any codes during that time? Was your idle of at all and did the car run fine when it was cold? IIRC most people end up throwing codes when the cranshaft position sensor needs replacing.