Light throttle stutter and brake question

[DOMO]

Hey guys I got a 2 part question for u guys. 06 2.0l sedan I'm experiencing a light stutter upon light throttle regardless of speed. I have no codes or anything and spark plugs are fine so I personally don't think it's a burning issue. Only thing I have noticed is that it happens with everything but a full tank of gas. Could this be a sign my fuel pump is on it's way out?

Second question is that I'm planning on going to the track in a few weeks and I was wondering if the 3's came with different sized calipers for the different trim levels. Mine is about as basic as you could get with the only thing power being locking doors. So is there a different size between the gt and I trim levels ?

Thanks in advance

 

[goldwing2000]

Easy answer is for part 2: yes, the S level trim with 2.3L engine has bigger rotors and calipers on the front. No idea if the S calipers will work with the I rotors, though. Rear brakes use the same calipers but the S has bigger rotors.

Part 1 probably isn't fuel pump. Fuel level wouldn't have a very big effect on that. Could be a TPS or ETB issue. Could even be an emissions/fuel vapor issue. Without a code, it's pretty hard to diagnose. If you can hook a monitor up to your OBD port, you can start looking at things and see what changes when the car is stuttering vs when it's not. I know mine feels like it stutters under heavy throttle sometimes when the A/C is on due to the compressor kicking on and off. Under light throttle could be something as simple as a dirty air filter, gunked up throttle plate, dirty MAF or even a clogged IAC. Also, when you checked your spark plugs, did you also check the rubber boots? If they're not properly lubricated with dielectric grease, the spark can travel along the inside of the boot. and ground to the cylinder head. Another notorious issue for these cars is the MAF sensor harness. The wires break inside the insulation and intermittently lose contact. That is even more likely to happen if you have a CAI.