Uneven Acceleration @ Full Throttle

[eldims]

Volvo S60 2.3T5 2003

I'm experiencing an uneven acceleration when i put my foot down on the throttle. Most noticeable during 4th and 5th gear. Just to be clear on the "uneven acceleration", it's when the car feels like it's accelerating very quickly at one point and accelerate slowly (but still picking up speed) at another point. The ups and downs happens every 2 sec or so with the downs in shorter duration. This only happens at full throttle and becomes smooth when i lift the throttle off a little. By smooth, i mean a more even acceleration, but obviously not at the quickest the car can or is supposed to go.

Base on what little knowledge i have on engine functions, I'm guessing a faulty injector in one or more of the cylinder causing lean mixture in that specific cylinder and a loss of overall power. This becomes more obvious at full throttle since at this point, the boost is at a level that the injector is no longer able to keep the A/F ratio at lambda. This is my speculation.

Anyway, i'm wondering if anyone has experienced this of might know what is wrong.

[D_V_ENT850R]

When did you change your plugs last. Check the gap. I would start there easiest and cheapest. Injector would show up all the time at idle and plugs or coils would show up under load. Other than that there are many possibilities.

[jimmy57]

Turbo control valve sticking gives that exact symptom.