hi I have a 1986 si civic with ZC engine. i have had a problem with it for a while. This problem is that it cuts out at 4 1/2 -5 thousand revs in first gear. This is only in first gear. i was getting a o2 sensor light but replaced the sensor and it went away but it is still cutting out. Does anyone have any idea what may be causing the problem. i think it may possibly be a vacuum problem or a problem with the speedometer.