Clutch Disengaging at high RPM?
 

On my way home today, all of a sudden my car starting losing power around 4000 rpm. Almost like it’s in neutral but not quite since the shifter is in gear and the pedal comes all the way back up.
If I stay below that, it’s fine.
I checked the clutch fluid and it’s full and in good condition. Also checked the other fluids while I was at it and those are fine.

Can someone help me figure this out? Dragging clutch maybe? Could it be the linkage? The clutch worked just fine until today.

Clutch slip ....... how many miles has the car done

86k miles. Does clutch slip normally happen so abruptly? I'd figure it'd be a gradual thing. This is my first manual btw...

It shifts fine but once I rev up to 4k it bucks and doesn't have throttle response...but back to normal once the revs drop.

Yep. Time for a new clutch.

Great time to upgrade to either the HDCSC or Z1's elimination kit. GL

Yup, no-brainer. The most expensive part of this process is the labor.

Might as well upgrade the clutch too, if only because I'd imagine a Z1 street clutch is probably far cheaper than OEM.

Hopefully, OP can find a shop that lets him provide the parts. ;)

Yeah I ordered the Z1 clutch kit, Zspeed HD CSC, and OEM Master Cylinder. For fluids I got Motul RBF600 and Redline MT85.

Sounds good! I am running the exact same setup with the addition of a Z1 lightweight flywheel.

So I changed the clutch, CSC, and master cylinder, refilled and bled clutch fluid...still having the original problem!
Could it possibly be the fuel pump?

I'm hoping the mech did the complete job; flywheel, pilot bearing, and installed the pressure plate. :icon14: Changing just the clutch disk, CSC & MC won't fix the problem, if you don't do the complete job. :icon14:


My vote is back to the mechanic. The opening for the fuel pump is behind the passenger seat, the FSM has the location. I've heard of some folks having the fuel pump head break off and drop the pump to the bottom of the tank. Phunk has the fix for that. GL

Isn't the pump at the bottom of the tank anyway? The head of the fuel pump assembly has springs so that when you secure it, it provides constant pressure holding the rest of the assembly at the bottom of the tank. I think the most dangerous thing that might occur when the head breaks is that the assembly is free floating around the tank. Considering the fuel level sensor is also attached to that assembly, it will lead to inaccurate fuel level readings to boot.

Also, seems unlikely that it's the fuel pump if the car is running. I think the fuel pump is running at a constant cycle, more or less throttle has nothing to do with the fuel pump (someone fact check me, pretty sure that's how it work). There should be a separate mechanism that adjusts fuel input into the engine.

OPs issue still sounds like a clutch issue to me. The mechanic should warranty his work considering he did not solve the original issue. Hopefully you told him about the issue and didn't just pop by asking him to change your clutch without context. A good mechanic would have taken it for a test drive to ensure that the issue is fixed before returning your car.

:iagree:


Which is why I asked if 'every thing' got done. I've never had a clutch problem reappear, if the complete job was done. When I was talking with Kevin @FastIntentions and we were discussing the clutch upgrade, I was all for surfacing the flywheel & calling it good. He told me that on our cars, it is a better idea to replace rather than resurface. The cost to replace is nominal in the grand scheme of maneuver. :)

I did the pressure plate but not the bushing or flywheel because they looked fine. I did it myself. It drove well at first but the next day on a cold start, the issue reappeared. I drove it today and it's fine again. Seems to only happen on cold start.

I think the fuel pump stays at a constant pressure like someone posted before. If not it should only have two settings (high/low). I don't think it's a fuel pump related problem though. If your car is not making a connection to the driveshaft it has to be the clutch or some other component related to driveshaft function. Flywheels have surface areas that can get worn as well.

No power above 4k RPM and bucking does not sound like clutch slip. With clutch slip your car will rev but not accelerate, worse effect in higher gears.

Any misfire or other codes? May be cam/crank position sensors, but codes would help narrow the issue down.

No codes. Could it be the flywheel since I didn't change that?

Is the car still revving and not accelerating or is it just bucking down around 4K?. I thought you said the clutch was slipping

revving and not accelerating. but there's a a sudden jolt when it happens. Also now that I installed the new clutch, I think it's sometimes still making contact with the flywheel when the clutch pedal is all way down because it's harder to shift. Could just need some bleeding for that issue though...

Hi, just noticed you mentioned you fitted the clutch yourself.
No idea of your mechanical skill level so please don't take this as any sort of a dig.
Could you have possibly fitted the clutch disc the wrong way around.
This could possibly explain some of your issues, if it is backwards, the hub of the clutch disc could be riding slightly on the flywheel, which would cause bad engagement & slipping under load.

I put the raised side toward the pressure plate, flat side toward flywheel. Just like the old one was positioned.

Couple more ideas for you to consider...
Plugged catalytic converter
Knock sensor getting tripped by some sort of vibration and pulling timing
Someone put a bad tune in her, verify you have a stock tune
Car thinks it's overheating
Maybe someone had the heads off and didn't get all the timing right when putting it back together.
Bad Gas
Water in gas
Plugged fuel filter


Get a cheap OBDII scanner and see what the engine operating parameters are. Not sure if a cheap one can read the knock sensor so maybe someone on here can recommend a good cheap one for you.

Imo it has be something wrong with the clutch /flywheel if it's revving and not accelerating. But I could be wrong

IIRC, all clutches come marked 'this side towards flywheel'. So it might not be an orientation issue. Flywheels can develop hot spots and heat cracks that are visible to the trained observer, but a person new to fixing cars might overlook. That's why everyone recommends changing the flywheel and pilot bearing, along with the clutch, pressure plate and throwout bearing (CSC in this case) when doing a clutch. Also, proper torque and proper torque sequence could be a contributing factor. Did you use a good torque wrench or did you use the 'it's tight enough' mode? I'm not trying to be rude, pressure plate bolts have torque ratings and sequence for a good reason. ;)


While DIY is a great way to learn and save money, IMHO, DIY on a clutch (especially since you said this is your first MT car) was probably not the way to go. It's time to bite the bullet and take it to a shop for professional diagnostics. GL.

I torqued it right but yeah I'll bring it to a shop.

Edit: I went to a local reputable shop, NM Imports, and they've done 5 370Z clutch jobs in the last 2 weeks. The mechanic was saying my CSC was probably going out before and now I need a rebleed. They normally tell people to come back after driving a bit to bleed it again. So I'll have them rebleed it since I used a power bleeder last time anyway...

Update: Turned out to be the flywheel as suspected. Thanks for the help!
Here's the old one. I replaced it with the Z1 midweight flywheel.
http://i.imgur.com/tLT1SbB.jpg