I have a 2000 Infiniti i30 with 160K miles that is in fantastic shape. I purchased it from a mechanic who had gotten it from a customer who basically ended up not wanting it. The mechanic replaced the idle air control valve and one of the six ignition coils.
After a few days of buying the car, I noticed that the car wasn't accelerating as quickly as one would expect an Infiniti to. Also, I was driving (probably around 50mph, and decelerating) and the transmission slipped, but was fine after slowing the car down, throwing it in park, then back into drive.
I took it into a shop after having pulled the DTC myself (code 1320), and we basically decided it would be best to replace all of the coils (minus the one that had already been replaced) and spark plugs, since they had never been replaced.
This improved acceleration considerably, but the car still seems to have trouble going from a full stop. It drives just fine, but it lags when it shifts between first, second, and third gear, causing a slight surge, or rocking back and forth as the gears change over. The check engine light is on, as well as the "SLIP" light. I checked for DTCs again, and I'm still getting 1320.
Any ideas of what might be the problem? The guys at the shop said if the coils don't fix it, then it may have something to do with the ECCS wiring harness? Any thoughts?