No change in ilde means the 3 cylinders concerned are not firing. Try swapping the coils with other cylinders and if the conditions migrates, the coils are bad.
The disconnecting of the ignition coils can trigger the fault.
DTC P1515: PREDICTED VS ACTUAL THROTTLE POSITION CORRELATION ERROR
Have the misfiring resolves and retest if the problem goes away.
SPONSORED LINKS
Tuesday, April 19th, 2011 AT 9:15 PM