A little background on the car, I've owned it for roughly 3-4 months, the car is a 2003 z4 2.5 5 speed, previous owner rebuilt and swapped in a 3.0 m54b30, I have lots of pictures on paperwork on the swap it was done beautifully. The car has no rear O2 sensors and has headers with no cats.
Recently it started to stutter heavily during acceleration, particularly in 2-4 gears, not in 1st or 5th. it was initially only from around 2k-3k RPMs, but have grown to the entire rev range. The odd part about this, it only does it when it's raining, or when there is colder water in the air, such as at night or early morning. I live in Alabama so our air is pretty hot and humid during the day, but it usually drives perfectly fine during hotter daytime hours.
People riding in the car state that the hesitation is like "when you slam on the clutch at 5k rpms on a hard pull and it jerks you forward", however the car is in gear the whole time at 1/4 throttle. I said it felt a lot like a clutch slipping, but it doesn't exactly seem that way. My main thought is the fuel pump or fuel pressure regulator, I plan on renting a fuel pressure gauge this weekend and testing it.
I have a check engine light for the rear O2s but nothing else. I've noticed that the trunk will occasionally leak in the back passenger side cubby, is there anything there I should look out for that could cause this? as odd as that is to look for I had a 2013 mustang gt, and the trunk would leak, and the fuel pump drive module was in the spare tire well, every time it rained it ran extremely poorly until I fixed the leak and replaced the module.
I have just replaced spark plugs about 2 weeks ago, any suggestions would be greatly appreciated.
Recently it started to stutter heavily during acceleration, particularly in 2-4 gears, not in 1st or 5th. it was initially only from around 2k-3k RPMs, but have grown to the entire rev range. The odd part about this, it only does it when it's raining, or when there is colder water in the air, such as at night or early morning. I live in Alabama so our air is pretty hot and humid during the day, but it usually drives perfectly fine during hotter daytime hours.
People riding in the car state that the hesitation is like "when you slam on the clutch at 5k rpms on a hard pull and it jerks you forward", however the car is in gear the whole time at 1/4 throttle. I said it felt a lot like a clutch slipping, but it doesn't exactly seem that way. My main thought is the fuel pump or fuel pressure regulator, I plan on renting a fuel pressure gauge this weekend and testing it.
I have a check engine light for the rear O2s but nothing else. I've noticed that the trunk will occasionally leak in the back passenger side cubby, is there anything there I should look out for that could cause this? as odd as that is to look for I had a 2013 mustang gt, and the trunk would leak, and the fuel pump drive module was in the spare tire well, every time it rained it ran extremely poorly until I fixed the leak and replaced the module.
I have just replaced spark plugs about 2 weeks ago, any suggestions would be greatly appreciated.
