Lately i have been having problems with random missfires. I will be driving and the car will start missfiring, bog down quite a bit and the check engine light will turn on. It never lasts for more than a minute or so and the car will never actually die. Once it stops missfiring it drives perfectly fine. It often happens more than once a day, sometimes mutiple times. I never have had this issue until my underdrive pulley was put on, so im wondering if it is a small timing issue. I plugged my tuner in to check the error codes and it reads random missfires. I replaced plugs, wires and did a complete tune up to cover all the minor basis and the problem continues. All i can come up with is maybe the guy that installed my underdrive pulley messed up the timiming slightly. If anyone has had this problem or can shed some light on this it would be greatly appreciated.
Oh and its on a 07 gt

 

The underdrives won't affect timing. It's read from a crank and cam sensor. However the crank sensor is down by the crank pulley. Maybe he cracked the sensor or damaged the wiring. Underdrives will also affect charging so make sure the battery is up to voltage. The underdrive install probably required removing the air intake tube. Make sure it is installed correctly {no pinched or rolled tubing lip at clamps which could produce lean codes} and the MAF sensor connector is plugged in correctly.