all right, my first post - hello there...

so i got myself a 95 Z28 with 80K miles on LT1 and 4L60e...
the only mod so far is a ghetto-looking cone air intake

now, heres the problem - at wot, when i get over 4200 rpms or so, i start getting a strange very loud rattling sound from the engine compartment, sounds kindalike the fangrinding on smth,but its not... i also thought itcould bethe intake rattling and i kindatied it down for now, so i dont think that is it...

also, it almost feels like a rev limiter, it dropps the rpms off by a few hundreed, kinda fluctuating between 4800 and 4200 or so, sluggs the power, and does not want to up-shift into next gear until i let go off throttle a little... but continues to make that weird rattling plastic sound...

if i dont floor it around or get above 4K rpms, it runs and drives groovy

oh, yeah, alsoits hard to start when cold - have to push down the throttle couple times and rev it up

any insights?

 

TUNE UP! New Plugs/wires and reset the timing will be a good start.

 

while i agree that tuneup is always good, i dont see what would be rattling like that and why it wouldnt shift and sluggs the rpms...

what do you mean by reset the timing?

 

i also read something about intake pressure having to be a certain number before it shifts... anyone knows more about this?

 

There is a good chanche that what you are hearing is serious pinging under load, especially if you are not using premium fuel. The loss of power is probably due to the computer pulling the timing back trying to protect the engine. Is the check engine lite coming on? The computer controls the transmission and will only allow certain gears if the engine is not running properly. Also give the car a tune up, fresh plugs & wires, clean filters, etc. The cone filter inside the engine compartment is a bad thing, as it sucks in the 180 deg air under the hood and promoting more pinging. Put the stock plumbing back in or get a cold air intake. Make sure th knock sensor is working properly and screwed in tight.

 

I thought that detonation actually gets better with a reduction of cylinder pressure by increasing the engine revolutions, decreasing the manifold pressure (throttle opening) or reducing the load on the engine... so it would detonate worse at low rpms... and i only have this problem at high rpms...

 

A larger throttle openingdecreasesvacuum which increases manifold absolute pressure on a normally aspirated engine,whichmeans that the throttle body is opening wider andallowing more air in the engine. This, and the engine "coming on cam" (torque peak) at those RPM,increases cylinder pressurewhich can causepinging or knocking. You can verify this using a scan tool, which would also show if the PCM is getting a knock signal and retarding the spark.

 

i do use chevron premium, and theres no engine light on, i will check the codes when i receive my ALDL cable...

i am kinda stuck on that cone intake thing... it is just this ricer-looking extension that goes to the corner where the box-filter originally was, and then there is a cone filter just banging around on the end of it all... i tied it up with a hose clamp so that it dont move around so much, but i have a feeling that this darn thing is the cause of it all

 

It won't hurt to take the filter off for a while to see what happens. The stock intake plumbing brings in cold air from the fender well, but it is restrictive.