Hey guys, long time reader here. I drive a 2005 Infiniti G35 coupe 6MT and have got an annoying problem.

While driving without parking lights or headlights the car runs and accelerates great. But as soon as I turn on the parking lights or head lights, the car suddenly bogs down and accelerates very slowly. I am not sure what it is. The problem only happens when the parking or headlights turn on. Also cruise control will not work (flashes SET light) when the above lights are on, but will work when the lights are off.

The check engine light does not come on. That's what is weird. I have some more observations. When the lights are on, the car will accelerate normally on the first 1/4 of pedal travel. After that car accelerates slowly the rest of the pedal travel. But it will accelerate as soon as the parking/headlights are off.

I replaced the knock sensor and sub harness. This problem still occurs. Any help will be greatly appreciated. Thanks

 

I got a multimeter to measure voltages. With car off the battery was at 12.8V. With car on but very little load, the voltage was about 14.4. With the lights, AC, and radio on, it was still about 14.4V. With car on, the voltage would sometimes go to 14.5V. Is the alternator starting to go out?

 

No sounds about right.

 

I have another observation. When I switched on the headlights on or added load, the voltage would drop down to 12V but quickly come back up to 14.4-14.5V. Is that voltage drop normal?

 

I figured out and fixed the problem. I have a uhaul lighting trailer kit. The grounding wire had come off of it and that was causing the issue when the lights turned on. The hitch is for a bike rack, but I figured it was a good idea to get the light kit anyway.