Loss of power MPG and Rough Idle
 

The car is 05' 350z Enth w/ 56000 miles.

Alright so the syptoms..
#1 Rough idle, around 450-600 it jumps alot and warmed up or cold it does not change also even with the AC on it still does it just not so bad.

#2 in the last 3 weeks since i replaced my flywheel and clutch for a lightweight flywheel and stage 3 clutch i have noticed about 60 miles per tank just poof, 12 gallons gets me about 170 miles and i say 12 gallons because i refill at 1/4 tank i refuse to let it get lower than that.

#3 when i first got the the car it ran amazingly but since then i have put some parts on it..
-Cold air intake
-intake manifold by kinetix
-invidia dual exh w/ x pipe
-headers
-test pipes
-underdrive pulley
-clutch
-flywheel

the car is very rough at idle and sluggish at low rpm's it is bogged down untill i hit about 3000-3500 rpms then it puts me in my seat like it should but around those rpms you feel an immediate increase in power even if im just earing my way up through the rpm's. also my gas milage seems to be the same as if i drive it easy or hard still the same per tank ( i did enjoy smashing a tank of gas lol).

So i have checked my intake system for leaks and also cleaned my MAF and that did not help the thing looked perfect before i cleaned it no dust or residue of any sort. also checked the oil and it looks perfect, i just replaced the spark plugs on the last oil change.


is my car just saying tune me?or what? im new to modding a car this is my first car i have modded. also the error code on it says its running lean in bank 1 and 2.

id check the intake manifold installation, fitment, and workmanship. Out of the parts you listed, thats probably the culprit.

i already check all that, i took it all apart and replaced the gasket on the manifold and redid the intake connections its none of that, i checked for cracks in the manifold and nothing. this is just a recent problem.

Honestly, id still be looking at that manifold...


Can you swap your stock back, and see if the issue persists?

Yes it still did(tried today), honestly the manifold has been on there for 4 years i would find it strange it would just now be an issue. but even with the stock one it made no difference.

Just re-read your OP, you say this started only after the new clutch? Were all of the other mods done previous to the clutch install?

Did you disconnect the battery to reset the ECU?

Yes everything was done previous to the clutch and flywheel, the last mod was over 6 months ago, also yes i have disconnected the battery.

Ive got to assume that the flywheel alignment is off, Do you have a way to check your ignition timing? OBD2 Scan app, or oldschool timing gun?

I did think of that but the thing was the problem didnt start untill 2 tanks of gas later so 500+ miles, and it wasnt like i was stressing the car at all with the break in period of the clutch, i did find a place with a snap-on diagnostic box so im gonna have that done next week. im thinking it could be a fuel pressure issue or even a bad injector because there is a consideral amount of carbon coming out of the tail pipes... much more than other z owners i have talked to.

Fixed...

Got it tuned and dyno'ed and every bit of my problems gone....

281.45 hpw
260?? tq

Not terrible....

got 17mpg in town and 29 highway again and it drives like when i got it w00t!

Did you replace any sensors (e.g., oxygen sensor , camshaft postion sensor, etc.). Your problem description is "classic" for problems with sensors. Your solution departs from what I would expect based upon your problem description, and that is why I ask for additional detail.

Honestly i didnt remove or replace anything since the problem happened, all i did was get it tuned. i tried adding some bad gas additive but that wast the issue.