Weird RPM behavior...

[MinisterofDOOM]

My car's been doing this for a while, but it only happens under such specific (and uncommon) circumstances that I've never bothered to look into it. Changed my mind today...tell me what you think.

The idle of the car will "jump" up or down a small amount (only ~500 rpm) when travelling at steady throttle (or very little more than that) between 2000 and 2500 rpm. Doesn't happen at any other RPM range. It's now definitely audible thanks to my Magnaflow, but I can also feel it...the car surges very slightly (probably not noticable to anyone who hasn't spent the last several years becoming familiar with this car). Any significant throttle increase, and the jumpy revs cease and the car goes back to normal...until returned to steady throttle@2000 to 2500 RPM.

This isn't causing any problems, but it is kind of annoying. It happens every single day on the stretch of road just outside my neighborhood when I'm returning home from work.

Things to note:Car still has original injectors. The car runs fine in all other conditions, so I'm not sure if it's injector related or not. The car has great pickup off the line (especially in the cold).I will be replacing them sometime in the next few months whether they give me trouble or not (I'm waiting until I nail down the necessities for the supercharger install so I can kill all that at once with the mani off and plenty of room).

Brand new NGK double platinum plugs and generic plug wires (maybe 1500 miles on them). (Has been doing this since before the plug/wire change)

New Walbro 255 lph Fuel pump (installed within the last 10,000 miles). I'm not sure if this problem existed before the walbro install or not. My perception of time is terrible.

This car has been so reliable mechanically that this is the first engine-related issue it's ever had (at 212k miles!).

[Beancooker]

I'm not too familiar with your car, but the first few things that come to mind aer; coil caps (or if you have a distributor cap and rotor, maybe the cap and rotor) Injectors? Doubtfull, but maybe the fuel filter? Vacuum line? FPR? The fact that it only happens between 2k & 2.5k make it really hard to diagnose. I'll keep the brain (or whatever substance that is between my ears) thinking about this one.

[craigvalk]

In other vehicles I've had those symptoms suggested a dirty throttle body.I would suggest spraying some Gumout or Seafoam inside there.. take off the air intake tube and give it a good cleaning.

Craig