i had the same problem a while back , i cleaned and tightened all the electrical connections and my problem disapeared (took a while tho) .there is a lenthy thread in here (somewheres )about it ,seems there was a lot of folks suffering with the same problem . changing relays ,solinoids and the like ,try the basic stuff first cleaning and tightening , a relay was about $10 ish ,a solinoid is around a $100 if i remember correctly. if you can find that thread ,theres lots of info . besta luck mate.
