Ok my mother in laws car is a 98 civic ex. Auto all stock. Its had this problem since she bought it. When turning the blinker on on driver side it blinks slower then normal no bulbs are out etc... but when I start making the left turn it will startspeerding then clicks off as normal when turn is complete.

passenger side is completely normal.

What couod cause this and where should I look first?

 

bad bulb. Have you even bothered to replace them?

 

No since I seen both work etc but ill switch them out and give them a try.