zimbo

iTrader: (4)

I have been experiencing a weird slight hesitation under WOT. It happens in the upper RPMs (5000 rpms) but does not happen all the time. I cannot describe it other than that it kinda feels like someone is just barely tapping the brakes.

Well, tonight I was in 2nd gear and punched it and somewhere between 4000 and 6000 rpms (sorry I don't know exactly when) there was a sudden jerk almost as though someone had slammed on the brakes. It freaked me out!!

Here are some things I've thought it might be:

- Some sort of engine problem. This is obviously the first thing I always suspect due to my paranoid nature. However, there is never any pinging/knocking noise associated with the hesitation I'm describing. I have no oil leaks, no smoke, etc. No other indication that it is engine related. The car idles fine, isn't rough. With the timing I'm taking out and my religious monitoring of A/F I don't think it's an engine problem.

- ECU pulling timing. I've thought that maybe the ECU is pulling a crap-load of timing and that is causing the hesitation. However, it seems too sudden (especially tonight) to be that.

- Blown piping connector. Once upon a time when I had the Vortech I had a fairly sudden jerk under boost along with an associated pop(!) sound and it turned out to be one of the silicon piping connectors had suddenly come loose at the intercooler. Obviously after that I could not see positive boost above 0 psi. Since I'm still able to generate positive boost at the expected RPMs, I don't think this is what happened tonight.

- Traction control system. The G35 has a "Traction Control Off" button that you can press to turn off traction control and I *ALWAYS* turn it off if I know I'm going to be boosting. However, the sudden hesistation I felt was VERY similar to the way the car acts if you forget to turn it off. I know it was off tonight, however. There are rumors that even when you turn this off it can still override your desires when it senses slippage. However, I don't believe I was nearing the limits of traction at the time--it was at about 5000 rpms in 2nd gear on a dry road. Also, the slip light did NOT come on.

- Wheel alignment issues. My front wheels are out of alignment ever since the turbo install. Apparently, the install requires doing something to the steering(?!) and my installer didn't get everything realigned properly. Basically, the steering wheel must be tilted slightly to the right in order for the wheels to be straight. It's not horrible--something I've been meaning to fix one of these days but the car is certainly driveable. Perhaps the alignment problem is causing the car to think it's losing traction?

- Slipping clutch. Not likely since the RPMs do not rise suddenly when the hesitation occurs and I don't smell anything.

- Nismo LSD. Just grasping at straws here, but my Nismo LSD has seemed much more "jerky" lately going around corners (at slow speeds such as in/out of driveway). When the rear wheels are "complaining" during such a turn there is a similar hesistation but I've always attributed that to the fact that one of the tires is being dragged sideways during the turn. Again, the fact that it seems worse lately may be attributed to the alignment issue.

Any other ideas? I'm pretty freaked out about this and am afraid to really "get on it" to troubleshoot further.

--Steve

dfw350z

Steve,

Are you still using the Alcohol Injection Kit? Could it be causing the issue you are experiencing? Has the temperature in your area changed dramatically?

zimbo

iTrader: (4)

Nope. My alcohol injection kit is not currently connected.

--Steve

dfw350z

I have heard yet not tried the removal of the fuse under the hood for traction control. Supposedly the system will still try and control traction to some degree. Have you tried this to eliminate it completly?

spazpilot

iTrader: (2)

it sounds to me like the car is going into limp mode but then coming out of it just as quick, unlike the z which will stay there till you reset the ecu or turn off the car and diconnect the mas sensor and reconect. are your running any piggyback where you can cut the mas voltage or is it similar to my setup were its just injectors and the ecu upgrade? If you ever go into limp mode you will know what I mean because you will think you have damage something serious. Spaz

booger

iTrader: (6)

Zimbo I have disconnected the DVC fuse with no ill effects . Its in the fuse box next to the battery . All your lights on the dash will light up though . DVC , slip ,brake , lights come on .

zimbo

iTrader: (4)

Limp mode was one of the things I thought of after I posted. Spaz, I know you had problems with that early on--but I hadn't heard of other people having that happen even with much higher boost/HP than I am running. Are other Greddy TT folks having to clamp MAF voltage to prevent this?

I'm running the PE kit with the TS ECU reprogram. I was at around 8.5 psi last night.

Booger, I'll try pulling the VDC fuse. However, I thought it was the same fuse as the rear brake light which I obviously can't pull.

--Steve

zimbo

iTrader: (4)

UPDATE: The car is DEFINITELY going into limp mode.

I tested again this morning and--sure enough--under full boost the car just craps out right at about 4500 rpms. It gets all "shuddery" and lifeless and stays that way until I turn off the car for 30 seconds or so and restart.

If I'm not under boost, there is no hesitation at higher RPMs. I have not yet tested partial boost because, frankly, it's an AWFUL feeling when limp mode comes on and I'm not totally sure what's causing it.

Last Friday I had test pipes and a free-flowing exhaust installed (basically just a Y-pipe to a 3" straight pipe with no muffler) so I'm obviously flowing more air but in my tests on Friday and Saturday I only felt very slight hesitation at 4500 rpms. Definitely NOT the full on limp mode like I did last night and this morning.

Does anyone else have this problem? I thought Spaz was the only one who had it and that it was caused by funky MAF placement.

BTW, my BOV is placed between the intercooler and the MAF. I know that the direction of the MAF housing matters (obviously) but does the position of the connector (i.e. its rotational clockface position) matter?

--Steve

booger

iTrader: (6)

No the brake fuse is in the fuse box down by your feet . And is just a small 10 amp fuse . The DVC fuse is a big one in the box next to the battery . It is clearly marked DVC

ravaz

iTrader: (1)

I had the same problems a few times myself. When I first installed the Greddy kit it happened two or three times when I would hit it hard, and then it happened again 2 weeks ago. I still have no idea what it was. Steve I want my ride still

zimbo

iTrader: (4)

In a PM, Spazpilot gave me more information about his symptoms: (1) if boost is above 7.5 psi, (2) and it's cool outside, (3) the car craps out at 4800 rpms and doesn't operate normally until the car is restarted. This is EXACTLY what I'm seeing.

So, now I need to talk to Technosquare to find out if clamping the MAF voltage will throw off my ECU reprogram.

{sigh} So many issues...

--Steve

booger

iTrader: (6)

Hope you guys find the problem . I didnt want to go the TT route because of the issues involved . But as you probably have noticed there are alot of issues with all FI . And Im wondering if this motor should be boosted at all . I guess i'll make up my mind on that when I get my comp. checked later this week....Bill

350Now

Glad you found the culprit. The Greddy TT if using the e-manage has the MAF voltage clamp to 5v. I can see it on one of the e-manage option.

THX723

iTrader: (3)

Steve,
Sounds like you're hitting saturation voltage w. the MAF ... causing limp mode.

With respect to your steering alignment issue, it sounds like the people working on it previously didn't properly align the steeing shaft to the spline. You should be able to fix this yourself. It is necessary to put your car on a jackstand, however. Just two screws ... pull out the shaft and re-insert one click over the appropriate direction.

Sharif@Forged

iTrader: (92)

This sounds 100% like limp mod. The car becomes lifeless until you shut it off. Try to find a method of clamping MAF voltage at just under 5.0V..like 4.97V or something like that. As mentioned, the eManage does this.

IceY2K1Max

iTrader: (1)

A Split Second FC1(or FC2) for $76 could clamp MAF voltage. It only requires battery, ground, and cut/splice into the MAF wire. http://www.splitsec.com/products/fc1/fc1ds.htm


TechnoSquare should start including these with their kits.

zimbo

iTrader: (4)

The silver lining to this situation is that I'm obviously getting more horsepower out of the free-flow exhaust than I was before even at the same PSI levels.

--Steve

Daking350z

Mine did that to me on 3 occasions in one day then never again...But I am SC @9psi and wouldnt max out the MAF until full boost at redline???Weird...Try replacing the plugs, and another thing you might want to check is for recalls on the crank position sensor..

teh215

iTrader: (8)

Skidazzle discussed this in this thread:

https://my350z.com/forum/showthread....hlight=voltage

gspot35

This happened to me when my R4 programming got of wack and was not retarding timing during boost. Obviously this sent my car into limp mode, but may not be relative to your situation since you have a flash, not piggy back.