weird problem!!!

ok, today when i was driving to work, my car decided that when i was goin down the highway it wanted to act funny.. well i was doin bout 80, and all of a sudden the spedo dropped to 65.. then spiked back to 80, and it did this several times. i checked the battery connections, and the battery guage read the same as it always does, its a newer battery, so that shouldnt be a problem right? maybe the ecm is messed up? i dont know what is going on.. another idea i had was that since im 50 miles over an oil change i'm gonna get that done tomorrow.. any ideas as to what may be wrong without me having to have someone check it out?

not sure if there is a known problem, but could be a broken speed pickup on the trans. on fourth gens are they gear or magnetic pickups??? cuz if its a gear driven speedo, the output shaft speedo gear could be cracked and loosening and tightening as it goes around, throwing off the speed. the instrument cluster could also be going bad.

here's the thing.. it doesnt affect the speed, and the acceleration is fine, it only decides to spike on the guage.. and only around 70-80 mph (never before).. i'm just more or less hoping its a small thing, because i dont have the money to fix it for another week..

well yeah, the gear im talking about isnt a major part of the tranny, has no effect on its working. its kinda an afterthought, slides down the output shaft and is held in place with a little metal tab, its a plastic gear on my car, i actually broke it taking it off, and now my speedo fluctuates at speed. but im thinking your car is a magnetic pickup, so its probly a small electical problem somewhere. just match the speed of traffic, and youll be fine.

i think they are magnetic pickups, but dont take my word on it...

My '98 Z28 is idling high, not starting right away, and is accelerating w/o me actually giving it gas. It sped up to 50 mph with my foot not even on the gas. The trip counter under the odometer is also resetting itself. Has this happened to anyone else?

sounds like possibly an IAC problem, as far as the trip odometer reseting, could be a circut problem. both are linked to the BCM i know that, the IAC goes through the PCM first, but id have to go through pages of technical diagnositcs before saying you had a bad BCM, but long story short, it sounds like an electrical problem, take it to the dealership.