Jeep Wrangler, 2003, 130,000+ miles: When I drive for more than 20 minutes, turn off, get out to an run errand, get in and start back up, I have these issues-it won't turn over right away and once I get going, say I am doing 50 miles per hour- the tachometer just drops to 0 - car still moving - then it wil go all the way up to 4 or 5 - a few seconds later everything normal. Check engine light goes on one day- out the next day and back on the next - WTF? Please help me! is it my computer? my speed sensor?? help me please! All started a week after an oitl change/tire rotation and a day after I got my car washed- coincidence?