problems with sonata 2003 v6

[esabban]

I have purchased the sonata 2003 V6 GLS, after 1000 mills the car started experiencing loss of power and when going up hill in third gear around 30-35 mills per hour, loss of RPM and power, adding gas would not result in addition of RPM and power, the car would increase speed slowly and when reached to around 40-45 mills per hour the RPM would suddenly go height, still in third gear, then switched to fourth gear. In addition spars have black carbon deposit on the inside of the plug, not on the conductor and insulator. Recently the car is bucking on the highway every now and then. Went to two dealers, computer does not show any code and they are dismissing all this as something being wrong with the car. ANY IDEA?
Thanks.
Eli

[Edited by esabban on Jul 16, 2003 3:20 AM]

[DSM-SONATA]

it sounds as though it's not a problem with your auto, as it happens on flat surfaces on the go, so check these;

leads are in good shape
maf sensor after air filter is connected properly
check that all clamps are tight
try resetting the car by disconnecting the battery, leaving it sit for 5 minutes, then reconnect.
do make sure that your water and oil is topped up.
try driving with the air con on, and the air con off, and see if that makes a difference.

from all of those, it sounds to me like either a lead or spark plug problem, or maf sensor is not plugged properly. if not have the dealer inspect;

coils are charing correctly get the dealer to check the output voltage
knock sensor isn't fouled
02 sensor isn't fouled
check timing belt is aligned properly