I own a 2004 Nissan Sentra SE R Spec-V with a cold air intake installed and a 4-2-1 exhaust installed also. The new exhaust has no precat and catalytic converter. Upon removing the old exhaust only 1 O2 sensor survived, the upflow (closest to the head). I went to the track and had 5 runs no problem, then on the way home it started misfiring and I felt a loss in power. I took the spark plugs out and saw they were dirty, I cleaned them with a wire brush then sea foamed the intake manifold, then I ran lucas fuel injector cleaner through the gas tank. The car doesn't misfire now but I still feel a lack of power. MAF checked out working perfect. I'm waiting on the down flow O2 sensor in the mail. Any ideas what might be the cause?
I also am getting really shitty gas mileage. After I cleaned it, the gas mileage increased by about 10mpg. I top out around 30 mpg at 55 on the highway. Any faster and it goes down about 2 mpg per every 1 mph.
have the same problem?
Wednesday, January 9th, 2013 AT 8:41 AM