This will sound nit-picky, but it's the kind of thing that bothers me.
I have a 2004 GP GT, NA. A few months ago I did a small tune up. The belt was wore, so while I had it off I also replaced the tensioner. At 145K miles, I figured I'd just be proactive about it. I aslo picked up a PCV valve and fuel filter. I have forgot about the fuel filter for about 80K miles, so I really thought I should add that on. The tune up went fine without any issues other than the fuel filter being pretty rusted on. After taking it for a spin, my butt dyno said it had more pickup and felt a little faster.
Fast forward 45 days or so. I've noticed that my acceleration just isn't as peppy as it was. On top of that, when I accelerate a little harder (like pushing up around the 3K RPM range and higher) it no longer sounds like a smooth arc. I hate trying to describe sounds, but to greatly exaggerate the sound, it goes like this: waaaaaaaaAAAAaAAAAAaAAAaAAAaAAA.... It's just these minor dips. It's not like a miss, but as if it just slightly dips in the acceleration curve. Those dips also get faster as the RPMs get higher. I can also almost hold the noise if I put the car in 2nd and drive at ~3000 RPM. It is not audible when revving in neutral. It seems to need a load on the engine to do it.
So it's not enough to trigger a check engine light, unfortunately. But it's audible if you shut off the radio. Part of my wanting to chase this down right now, is that I'm thinking of selling the car and I don't want to pass off a problem to someone else. The tensioner feels good, the PCV valve has it's o-rings... I can't say much about the filter expect it's not leaking. Any ideas?
