Hello. i just went out for a cruise... went WOT and the car would hesitate/bog at 5500 rpm... as if i hit an early rev limiter. i thought it was the VDC kicking in, but the light wasn't on. tried again with the VDC off, with the same results. then, i released the gas and the car now has some nasty sound to it! it sounds like a tapping noise... like a key to a metal door. the tapping noise is relative to the rpm levels... so i am thinking it's something regarding the engine or the transmission (flywheel?).


a few things to know:
- the car was fine before i had a clutch job... this happened AFTER the clutch job of an RPS street max with JWT flywheel
- stock bottom end of engine
- no SES lights were on and no noxious fumes/colored smoke from the exhaust before and after the hesitation and tapping symptoms

does anyone know what could be the problem?

andy.

 

quick guess...detonation, bend rod

what size injectors do yo have?

 

i am using the stock injectors supplied by APS.. i am thinking 440cc? the car was never tuned either... it's pretuned and 'safe' out of the box.

 

That would be my guess also. I don't think bent rod...YET

 

i really hope it's not a bent rod!

i went to diagnose the problem... the ticking sound is coming from the front of the engine, where the pulleys are located. the sound is also loud from the top of the engine/plenum. through some research, i am thinking the timing chain and tensioner or perhaps the valves doing the buck nasty to the pistons? the crank pulley is not wobbling either.

i guess the only thing i can do is take it to infiniti to have it checked out. bummer...

thanks for the help guys.

edit:
i wonder what cylinders bent rods are usually located in... wouldn't a bent rod emit sounds at the bottom instead of the top of the engine?

 

Do you have an aftermarket pulley?, what weight/brand oil do you use?

 

no i don't. all pulleys are stock.

 

Diagnosing noises is an impossible prospect on the internet. It could be a whole host of different things. Do you have a local shop that can check it out for you? I'd suggest taking it to Gt Motorports...probably the best shop in the LA Area. www.gtmotorsports.com Ask for sam, and maybe you could swing the car by for some trouble shooting.

 

thanks for the reply sharif.

the nearest 'shop' is the infiniti dealership. gt motorsports is around 20 minutes away... however i don't feel that my car is safe to drive in prolonged duration with this 'ticking' noise. seems like something is hitting against each other...

 

If its a definate loud metal on metal noise, that yes...dont drive it. Try to have to towed to GT Motorpsports, or give Sam a call...maybe you can arrange towing for you.

Hope everything works out fine, but Sam is a genious with troubleshooting stuff, and he will figure out the cause of the issue. Hopefully its nothing too serious.

 

sharif, thanks for the words of advice. i contacted my dealership instead for safety reasons. got an appointment tomorrow morning. so all is going according to plan.

well, this thing was bugging the crap out of me, so i decided to take the initiative. i plucked out the 4 ignition coils, one by one, that is near the symptomatic area. cranked each time in between the plucking and replacing. the sound still persists. i decided not to take the 2 closest to the firewall, because it's furthest away from the affected area and just a PITA to take out.

after replacing all the coil packs in, i listed more attentatively... the sound was emitting from the driverside bank, front and top. i also checked underneath the car and it sounds the same. it sounded like BB pellets shooting outward from the head and into the plenum, 1 BB at a time at the appropriate rate as rpms increase or decrease... that can't be a knock or slap, right? all in all, i am around 68% confident that is not a spun rod bearing problem! it's not much, but i am happy i found SOME closure.

i distinctly remember a big bog that violently shook my car as if i hit the rev/fuel limiter at 5.5k rpm, right before i got this problem. the shock could have displaced the driverside turbo exhaust piping, inducing a tiny tiny exhaust leak.

so.. i have a few cases:
- could be a faulty chain tensioner, as in veilside350zTT's case
- could be valvetrain booty knocking with the pistons, or by themselves
- could be a simple gas leak from the manifold/turbo/downpipe

let's just hope the problem is one of these 3 cases... *knock on wood*

 

This doesn't sound good, get it to a qualified tuner asap. Most likely all damage is done but try to prevent further damage.

 

I think I'd prefer to just pay some extra cash to have it towed to the shop Sharif recommended. I don't know about LA, but in Tampa the dealers wouldn't know the first thing about a turbocharged Z.

 

Sometimes a good mechanics scope can help (like a doctors, but with a long end). Or use a screwdriver to amplify the sound. This is by no means a great way to diagnose, but it will get you a much better idea of exactly what the sound is, and exactly where it is coming from. I would bet against an exhaust leak, it seems like it would be in the valvetrain from everything I've read. But again as mentioned before, impossible to offer an educated guess without hearing it in person.

 

the symptoms are general automotive troubleshooting.. not just FI specific. i am pretty sure the dealer can at least pinpoint where the noise is coming from. if it's turbo related, i'll have the car towed to GT motorsports. they have worked on my car before and i must say... great service and honesty.

 

Where ever you decide to take it...please tow it. There were a couple members that drove around just a few miles with ticking and knocking....and now they have holes in the sides of the blocks. Please be safe.

 

agreed. motors are not supposed to make those sharp metallic sounds. if they do it is because what ever it is has not gotten "caught" in between other parts yet and caused failure.
i will step out on a limb here and guess you detonated and broke some ring lands in big fashion. i will guess you started to detonate and when the ecu was pulling timing you detonated big and thats when you felt the stutter. but you would be getting some smoke most likely. when you had the coil packs out it would have been good to pull the plugs also and do a comp check.
a bent valve is no joke either. every time it hits the seat again it fatigues the valve and it will snap off at some point (maybe next start up, maybe next month) but it will!!! that will destroy the block, and atleast one head, and prolly more.
if you knew for sure the sound was something simple or not detrimental to the long block, then you could drive to get checked out. but from what you are describing, it may be not such a good thing.

 

do you have a utec or unichip? this is the exact thing that happened to me.. its not a loud noise right? just a slight tack tack tack.. noticible but not like a rod slapping.. sounds like a valve? well my car did the same thing at that 5,500 rpm and i had the same result.. i parked my car and then tried to drive it to mrc and it blew on the way.. what happened was the rings went from detonation and then my piston incinergrated on the drive to the shop.. good luck man and let us know