TheCajunStyle

iTrader: (6)

I had the first big issue with my F/Ied Z today. Here's the quick story: I was in 4th gear at approximately 4000rpms, hit WOT, at 5000rpms car went into limp mode. (Could not accelerate past 2000rpms). There was no audible detonation, no smoke out the exhaust, no unusual noises at all. I felt no misfiring; the ECU simply went into limp mode. I pulled into the breakdown lane, turned off the ignition for about 2 minutes and started thinking the worst... Luckily, the car started right up, but have a very shaky idle. "Service Engine Soon" appeared. After about 30 seconds of idling, I decided to continue on my journey--but staying as far away from boost as possible.

Since it's Friday night, my shop (Performance in L.I.) is closed and access to an OBDII scanner isn't possible at this time.

Here's a quick synopsis of events leading up to this situation:

A.) Thursday--attempted driving my car into a 2 car garage that has a very high lip at it's entrance. I was entering VERY VERY slowly because of this reason, and could hear something scraping near the "M" brace on the bottom of the car. I decided to slowly back out of the garage. Ever since that event, I've had a somewhat louder exhaust noise and have also had rattling under heavy acceleration. Something could have been bent (or cracked?).

B.) Filled up my tank with 93 octane (from Shell) today before taking this little drive during which my car went into limp mode. The distance travelled to the highway from the gas station was about 15 miles. I did not hit boost the entire way to the highway. Once I got on the highway I hit full boost for a few seconds, then at 5000rpms, I go into limp mode. (Bad gas???)

C.) After getting out of limp mode, I discover that I now have a new issue that never existed before: car will stall while in gear at LOW rpms (<1000rpms) which the clutch fully depressed. For instance, pull up to a toll booth, car is in 1st, clutch all the way in--stall. If I physically put the gearbox in neutral, the car does NOT stall at low RPMs. (Clutch adjustment needed?)

D.) While driving my car home after recovering from limp mode, it now has an audible single backfire when I release the throttle at 2700rpms. I am able to repeat it.

I have the JWT TT kit installed. No other performance upgrades are on the engine. I had the kit installed at 6,000 miles and have logged 9,000 HARD miles on the car since then. Spark plugs were changed from NGK-R (heat range 5) to NGK Iridiums (one-step colder). The old plugs removed had normal wear on them and never misfired. The new plugs, as well, have never misfired. I change my oil every 2,000 miles. (Last oil change occurred 1,000 miles ago).

Alrighty, thanks for reading this NOVEL. I just wanted to provide as much information as possible hoping that someone might be able to help. I'll contact Performance on Monday to set up an appointment to further investigate what's going on...

Thanks for your help!!

John

superdude

iTrader: (2)

get ur idle raised will correct the stalling, thats what happened in my car.

bad gas? never heard of bad gas before. unless the guy filled it up with less of a grade, in that case use an octane booster.

Navygolf13

iTrader: (5)

Not sure about the stalling issue, but I know the limp mode is something that happens when the MAF is overloaded.

By the way who did the install?

TheCajunStyle

iTrader: (6)

Performance Motorsport did the install--I've had ZERO problems for over 9,000 miles now. I did speak to them today--they believe the MAF was overloaded due to the drop in temperature last night. I've been driving the car in 70+ temps all spring/summer and last night dipped down to the low 50s. The ECU wasn't expecting that...

I'm going out to pull the negative terminal, we'll see how things are tomorrow!

Beer Goggles

iTrader: (2)

Why not jack up the car and see what you messed up. Obviously if you hit something and it's now louder, and it hasn't run correctly sense you ripped of crushed something that made a change. Go under and look for crap you messed up.

kjbalto

I had the same exact problem. I also have the JWT kit and was the first G35 they did at Performance Motorsports. Only my problem happened last winter and it was a very cold day. My car went into limp mode and I pulled over. Shut it off for a minute, started it back up and it was fine. It happened again twice more that night but after that it never happened again. I didn't have to bring it back to PM. They said the same thing to me about the weather being cold. But the low 50's isn't considered cold. LOL The day it happened to me it was like 15-20 degrees out. They said JWT's stock tune is for Cali weather, or something like that.

TheCajunStyle

iTrader: (6)

Okay...I disconnected the negative terminal overnight, allowed the car to fully warm up and took it for a quick drive. No dice. Same issues. Car will not go into boost at all. A lot of fuel is being dumped and causing some backfiring when I let off of the throttle.

I got home and pulled three codes:

P1271 Air/Fuel Ratio Sensor 1
P0340 CMP (Cam Shaft Position) Sensor (Phase)
P0345 CMP Sensor (Phase)

Ouchies.

I'm going to get my car up on jack stands tomorrow to see if I ripped out an O2 sensor... I sure as hell hope not.

k3silk

iTrader: (12)

hope everything is good.

Julian@MRC

iTrader: (28)

With the cooler weather, your car is prone to making more boost.TheJWT uses the split second box, which is not capable of compensating for pressure increases, as it is not a MAP based tunning system. What could have happened is you made more boost than normal, and maxed out the MAF sensor.However if this were the case, the car would start back up and run fine afterwards.
Another scenario, is you got a crappy grade octane gas or bad gas,and detonated and cracked a piston. This happened to a friend of mine after he had it tuned and filled up at a different gas station. One way to tell is pull the plugs and see if one is coated in oil or bent..
And yet anothe scenario is a bent or toasted valve, which might cause the cam sensor codes..
And yet another scenario is when pulling in the garage you craked your crank position sensor which is on the bottom of the tranny, which can cause a plethela of weird things to take place..
Your problem is best diagnosed in person, and not over the internet as there are at least a dozen different things that could be bad..

TheCajunStyle

iTrader: (6)

Julian, I agree with you. I will have my car up on jackstands tonight. It's a long 3 hour drive to Performance for me, so I like to see if anyone else has had similar issues first... Yes, after seeing what the codes were, I believe you're right, time to go to the shop!

Sharif@Forged

iTrader: (92)

Was the boost raised on this vehicle? The split second has no MAF clamp that I can find....so if the boost is raised, and/or if too much fuel is added prior to 4600rpm, the car will go into limp mode. There are ways to work around it, but I would check your boost level and report back. Boost levels can charge slightly with different ambient conditions, so those minor boost fluctuations might be triggering the limp mode. The codes you got, are likely just phantom codes, that were trigger when the car went into limp, and are not necessarily indicative of a problem with your cam position sensor..etc..etc.

best of luck.

TheCajunStyle

iTrader: (6)

I'll report back after I get pictures (tonight). I think anything else is just conjecture at the moment.

Julian@MRC

iTrader: (28)

I would agree with you on this, however, he did say that the car conytinued to run like crap and back fire after restarting.Generally limp mode resets itself on the next drive cycle.Therefore I am leaning towards an actual problem in the car as a result of overboosting.. Look for Oil on the MAF wire also, if your getting blowby the oil can make itself to the maf wire and screw things all up also..

Starchecker

subscribing

TheCajunStyle

iTrader: (6)

Julian, limp mode did in fact reset itself after the restart, but, yes the car ran like dog... I was very reluctant to try this, but when I made an attempt to go into boost, limp mode re-enabled itself.

I'm on the stock internal wastegate springs (6.8psi). I've made no attempt to raise the boost, so it's a completely out of the box install... I'm not good at troubleshooting F/I issues like you guys are, but I'm not sure how I could "over-boost" (since there's nothing controlling an actuator).

I will check the MAF sensor for oil tonight, I'll pull my plugs, and provide some photos of the undercarriage...

One question though: the MAF is located in the stock location--directly following the air intake filter... (it's not located on the intake manifold inlet). How can oil get all the way down the intake tube on the MAF sensor?

I think the first OBDII code is the one to worry about... From the FSM, the CEL appears on the dashboard when ~0.0 volts are read from the exhaust manifold O2 sensor (indicating a sensor failure). This would really f-up the AFR, in my opinion. Why the sensor failed is beyond my imagination.

I'd love to get out of work early so that I can post here (before you guys leave for the day), but I won't be able to get to it til 7pm. Again, I'm not too worried--the car runs perfectly fine if I'm driving it like a grandma, or letting it idle...

--John

SleepyZ

iTrader: (1)

Ok, just my 2 cents here. Not sure if your problem was solved allready. I was having issues with my Z going into limp mode and it kept throwing the cam and crank possition sensor codes. After changing 3 crank possition sensors myself, I got on the phone with VRT and they decided to try rewiring the piggyback computer that was installed. It fixed everything. I dont know what computer you have installed but just letting you know. It is one of those longshot from left field kind of things but thats what went down with mine. Good luck

TheCajunStyle

iTrader: (6)

OK quick update:

I took photos of the undercarriage. Everything looks to be fine. I pulled the spark plug that is on the passenger's side, closest to the firewall. You'll notice some carbon from where I pulled the spark plug out (due to all the backfiring?)... Anyways, that one plug looked fine... Should I be pulling all the others?

I'll be making an appointment to have this checked out ASAP.

PHOTOS:
http://www.leftysworldfamous.com/z/

Sharif@Forged

iTrader: (92)

A little carbon is fine, as FI engines tend to run a little bit rich at WOT. My money is still on the MAF clamp/overload issue.

TheCajunStyle

iTrader: (6)

Sharif, that's what my shop thinks (I see you do as well...)

I just wish there was something I could do to avoid having to make the 3 hour trip for something that seems so simple.

I'm wondering if I should actually "clear" the OBDII codes... Does the mere presence of a code cause the ECU to act differently? As far as I'm aware, an OBDII code is used only for user feedback and NOT used for any calculations that the ECU might perform.

My whole point here is, what can the shop do to remedy this MAF clamping situation that I (as an average Joe) can't do in my garage?

--John

35ounces

iTrader: (5)

Well if thats what it is then it should not keep happening everytime you hit boost unless it is purely due to the colder weather. We are supposed to get some warmer weather over the next couple of days so you can see if it makes any difference. It just is a little odd that you were running perfectly and then after you scraped the car has had issues that are repeatable. My money is on the crank sensor.
I'd clear the codes and see if the exact same codes come back.

Be careful.