My 88 420 starts fine. For the second time in a month when first starting out the ABS warning light comes on and the idle jumps to around 1100, from the normal range of about 7500. All other items (temp, oil pressure, etc.) are normmal. The weather is nice, about 65 degrees with no rain. After about 5 minutes the light goes off and the idle returns to normal. I cannot figure any connection between the two. Is it electrical ? where is the connection ? Any help or ideas would be appreciated.