Last night I went somewhere an hour away.. Took care of business and when I started the car , idle was rough and sounded weird. Constant audible thuds/clicking from the engine bay and I could feel the vibration as well... It sounded like really loud cams... Pushing the clutch didn't change anything... But, when I slowly revved the engine, the constant thuds/clicking noise and vibration went away once RPM went above 1000rpm.

Although it was stupid of me to drive back, I did and the car drove fine.. After driving on a highway for 30 min, I exited and stopped at a stoplight.. Idle was perfect.. no noise, no vibration.. I came home and reset the ecu, and performed throttle position learning, and idle learning procedures.. Car seemed to be fine..

Then this morning.. it all came back!! What's going on here??
Can low oil level possibly be the cause of this? My APS sump pump leaks a little, so I need to add oil periodically... I should add oil and see...
Since it's driving fine above 1000rpm, I don't think I bent a rod... what do you guys think?

 

Might be low on oil.

 

So the issue only occurs on cold start? I would say it could be a bad rod bearing but that usually is evident when the oil has heated up enough to thin out.

 

My car kinda did the same thing as yours. After a day of driving it the noise was at any RPM and ended up being a spun rod bearing. I am not rebuilding the motor. IF it is a spun bearing STOP driving the car, so you might have a chance of saving your crank.

 

Yeah I guess noise is only there before the engine warms up... I added oil just now and I'm gonna let it cool down for 6 hours before I start up the engine again.. Is there any other ways to tell it is indeed the bad rod bearing?

 

That's not a good news... I hope it's just a low oil....

 

Let us know if you find anything concrete.

 

Pull the oil pan. If you got shavings then its probably a bearing.

 

Is this like a misfire, could you just have a bad coil?

 

if it was a bad coil it wouldnt tick

 

No, I don't think so.. the noise was in sync.. like the cams ticking noises. but louder..

 

It will usually make a marbles in a can noise at idle and the noise will be rpm dependent. Usually the cause is detonation impacting the piston when it is on it stroke upwards. This pushes down on the rod giving the rod bearing just enough space to move.

 

Just thought of something, has anyone experienced a loose timming chain? I am pretty sure the chain tensioner is hydraulic so you could be getting some chain slap on cold start and then when the tensioner buildes up enough hydraulic pressure the chain tightens.

Don't take this word for word, but just an idea i am throwing out there

 

Did you use an oil filter without an ANTI-siphon valve, that would lead to dry start and lots of noise.

Also the one person that I knew that was Turbo had a coil go bad and he thought he ruined his car too.

 

I never had a problem with oil filter valve... I changed oil 1500miles ago..
If a coil goes bad, shouldn't it make noise all the time, since it causes misfire?

 

I'm assuming it could be almost bad, where it would have problems when cold.

What oil filter did you use?

 

just a thought. he could have a bad lifter. try using a thinner oil

 

ARGH!!!! The noise is still there~ I started up the car after cooling it down for 6hours.. Noise was there for about 10 min, and it disappeared once the car warmed up...

Could it be the VVT sprocket issue????? There is a TSB out for this problem!!
Sam at GT motorsports mentions it here:
https://my350z.com/forum/showthread....ts+short+block

 

i hate to say it bro but that is exactly how my car sounded when i bent my rod/s.

 

So your ticking/thuds would disappear once the car warms up as well? This is just too strange... The short block I bought off from one of the members is being shipped to GT Motorsports as I type this... So, I might be in the same boat as you... I was already planning on building the engine, and this happens....