A successful attempt has been made to analyse about 6000 single pulses of PSR B1133+16 obtained with the 100-m Effelsberg radio telescope. The high-resolution (60 μs) data were taken at a frequency of 8.35 GHz with a bandwidth of 1.1 GHz. In order to examine the pulse-to-pulse intensity modulations, we performed both longitude- and harmonic-resolved fluctuation spectral analysis. We identified the low-frequency feature associated with an amplitude modulation at , which can be interpreted as the circulation time P4≃ 30 P1 of the underlying subbeam carousel model. Despite the erratic nature of this pulsar, we also found evidence of periodic pseudo-nulls with P4= 28.44 P1. This is exactly the value at which Herfindal & Rankin found periodic pseudo-nulls in their 327 MHz data. We thus believe that this is the actual carousel circulation time in PSR B1133+16, particularly during orderly circulation.