just recently installed stereo system to car..

Front: 6.5 Option Audio splits
Rear: Fusion 6x9 Reactor
Sub: Sony Explod lol
Head Unit: Kenwood
Amp: Audiomaster 1000W 4 channel (some cheap amp from WOW)

but anyway everything is awsome when the key is turned, and engine is off

then as soon as you strat the car there is a hissing/whining noise coming from the left front passenger side, the noise is coming from what seems to be the tweeter and woofer.... the noise gets worse and louder as the car accelerates

whats the problem?

Engine noise. If you got it installed somwhere then bring it back. Otherwise, someone on here might be able to help you troubleshoot it. Better check all your grounds and make sure your signal cables aren't too close to power cables. Also try swapping the RCA cables from left to right to try and isolate where its coming from.

ok as of today i separated the 12V cable from all the speaker/audio cables and ran them separately through the cab... it still seems to happen... though not as bad, it is only audible when driving without music

i think it might be the head unit ground... coz it stops when i put the head unit on standby... likely?

i got this problem too.. if anyone can tell me how to fix i'd be very happy.. i thought it was just cos i got a ebay headunit..

got this problem with 2002 tj .
i know it got better when i got my aircon /water pump and psteerin belts replaced
still not 100% but bearable now, it was pretty bad beforehand .
is factory standard set up , pity because im reluctant too upgrade without doing away with this problem .
any body know how to fix wouldbe good thanks

Alternator whine, used to be a common problem long time ago.

Check the alternator connections - battery disconnected first - or put a "hash filter" on the 12 v feed to the audio stuff. Shouldn't be happening with a standard setup though. There is a filter/capacitor on the outside of the alternator itself, I believe.

My TJ has no problems, nor have any of the Magnas I have owned, TJ was fine with the original deck and the current (cheap) Pioneer deck. Check that the deck is earthed correctly, as well as the aerial cable at both ends. An unearthed aerial cable will pick up noise seeing it runs the full length of the car.

Like I said, used to be a common problem, but it was sorted years ago by the manufacturers and shouldn't be happening.

It can be a sign that the alternator is on its last legs, with the brushes not making good contact with the armature and generation a lot of sparks and electrical noise in the system.