Hey guys, I have a 03 350z touring with 76k miles, intake, plenum spacer, test pipes, and JWT stage clutch/lightweight flywheel that is barely a year installed. I have a few problems I don't know if they're all connected.

I've noticed a substantial power loss, I had a CEL for my knock sensor which I thought would fix everything but after getting that along with an oil leak fixed nothing changed. The cars throttle response is very lagged, my buddy with same car n mods said you wouldn't know it had a lightweight flywheel if I didn't tell him. I notice some smoke coming out of the exhaust when I floor it and it idles funny, if I slow down n push in the clutch the car almost dies before I idle, and sometimes when I turn the car on it will die out and ill have to rev it a little when I turn it on.

Also the car will randomly go into safe mode for like 30 seconds and the check engine light will flash, then as soon as I hit a certain rpm it just stops and runs smooth. The Rpms will even almost die out when I roll the windows down or first turn the lights on, but more than normal.

I'm tired of dumping money into it and having no idea what's wrong, anybody that can help it would be greatly appreciated and thank you for taking the time to read all this!

 

Honestly....sounds like a cluster f^@k of problems.
And what color is the smoke? Blue or white? n does it have certain smell to it?

 

Did you scan for codes recently ?, Maybe you still have a ghost code for the knock sensor which is very common if you didn't change the harness.

A flashing CEL indicates a misfire, Could be plugs, coils, injectors, vacuum leak, etc ...

 

I'm pretty sure it's white but not positive, it smells like unburnt fuel but more than the normal amount you would get from test pipes

 

I haven't but I will do that today, if its a cylinder misfire is there any way to narrow down the problem without fixing everything until it works lol. It's weird there is always a power loss but it doesn't always do the misfire it only happens once in a while

UPDATE: I just did it the obd2 scan and it says CEL CODE
P0327 Cnf knock sensor circuit low input bank 1, also says mod10

 

I never replaced the harness, just the sensor. More research suggests the P0327 code is usually a result of a bad harness. I heard from the mechanic that the knock sensor itself was a b***h to get to, could the harness really be making it run that lousy!? And if so, how difficult is the harness to get to when you replace it?

 

The knock sensor is placed under the intake runners, You have to remove the upper and lower intake manifold then the runners to get access to the sensor. It's an easy job if you know what you are doing.

The harness is a part of the injectors harness, But Z1 sells the sub harness only.

350Z / G35 VQ35DE Knock Sensor Sub Harness

 

Here's a pic showing the other end of the KS harness,

 

I actually have the entire electrical kit for the car I needed cuz I needed part of the mad sensor harness, it's used off a other Z my mechanic got them. But the injector harness and everything is sitting in there, should I give it a try or just buy a new sub harness?

Also thanks for the detailed response man!

 

Considering that reaching the sensor is a time consuming job, I would just buy a new harness.

 

I ordered the wiring harness, how much generally is it in labor if I paid a shop to replace it?

 

*** what engine mods do you have???

 

Fujita SRI, berk racing test pipes, Motordyne plenum spacer, and JWT stage 2 clutch n lightweight flywheel

 

Maybe u should try cleaning ur MAF sensor first of all since u have an upgraded intake which u probably have to oil the filter or something, which does cause the sensor to become dirty easily. This will hopefully allow the sensor to get a more accurate reading of the airflow and help out with the lag. As for the idling/stalling out problem, u may want to look into cleaning ur TB. Your car should run smoother after that. Be sure to disconnect the battery before cleaning everything, and do the relearn procedures after cleaning and hooking everything back up.
CRC throttle body/intake cleaner $6
MAF sensor cleaner $5
Relearn procedures. 2-5 minutes
Good luck man. Oh and maybe look into and research if u should reprogram ur ECU since u have a couple of bolt ons. Doubt u need to tho.

 

Thanks a LOT man this post was very helpful, I'm going to to do both tomorrow! Are there any links on how to clean ur Throttle Body?

 

You can search for it on the forums or google, but pretty much; disconnect negative battery terminal (if u wanna disconnect positive too for "extra measure", go ahead, but negative first. And to reconnect, vice-versa. And clean off any rust with a wire brush that could be preventing a good stable connection). Next, take off the intake tube(careful w/ 10mm bolt on left side, and the vacuum hose connected under. Check the vacuum hose for cracks actually lol). After you've exposed the tb, disconnect the wire harness from it(don't try yanking it off, u have to press down a tab to pull it off. Should come off easily). All that's left is removing the 4(four) screws holding it in place with an Allen wrench(long-ish allen wrench to get the bottom screws) and pliers for leverage while unscrewing. Those things are screwed on pretty tight
After removing the TB, just give it a little (or lot, upto u) bit of spraying(try not to spray the connector for the wire) and use a rag or old t-shirt to clean off all the black. U may need to repeat the spraying and wiping steps a couple of times lol. If u prefer being more gentle, which u should be since the butterfly is supposedly sensitive, spray the cleaner onto the shirt, then clean away. Use this method to lightly clean the... Idk what it's called, upper plenum? What the TB was connected to. That thing lol sorry. WARNING: it's been reported that cleaning the TB and moving the plate messes with the idle(high idle, 1200 RPM usually). From my experience, I really wanted to clean it well, so I moved the plate to clean almost everything and was totally fine afterwards (I think as long as the battery is not hooked up, you should be fine. But I'm just giving the warning). While the TB is drying off (be sure to let it dry) from its cleaning, might as well clean ur MAF sensor since the battery is disconnected already. Just remove the harness, unscrew the two screws, and be gentle with it. Spray it as instructed on the cleaner. Here's a thread, post #38(by mr. amr_electron up there XD lol) shows u where to spray:
https://my350z.com/forum/maintenance-and-repair/200141-anyone-clean-their-maf-mass-air-flow-sensor.html

After u let everything dry, and have checked ur intake/hoses for leaks. Install ur TB AND harness, MAF sensor AND harness, put ur intake back on(secure vacuum hose onto it first). After you've checked and double checked that everything is hooked up properly, connect the battery back up, do the first two relearn procedures(the third requires a warm engine), and start her up let her run for a bit(burn whatever cleaner/chemicals that remained on the TB/MAF). If u think u need to run the third relearn procedure cuz the idles a little funny(most likely not), it's there: https://my350z.com/forum/maintenance...procedure.html
Sorry for the long read. Hope it turns out good. You're more than welcome to do ur own research on how to do this, and confirm what I've said good luck.

 

Ok so update, got my knock sensor harness installed. The guy said whoever did the knock sensor before messed it up, something about it being torqued way too right, they actually crushed the sensor harness between the intake so the intake was leaking and the sensor was almost severed, and they used all the same gaskets so he swapped out all the intake gaskets and the throttle response is MUCH better.

The ONLY problem still is the idle is low and kinda rough. It's barely to 500rpms and when you rev it it almost dies when it falls back down. To the point where when I rev match before a turn to downshift I can feel the power steering weaken when I go to turn because it's almost about to die. Also when I start the car once it's warm, if I don't gas it a little it will just die right out.


Anybody have any ideas as to what this is?!

 

If u haven't done the above suggestions, u may want to try it. Only other thing I can think of is a cracked vacuum hose(connected under the intake tube).