fluctuates as it warms up? So I have been having a problem with my 1990 Honda Accord. When I start it up my rpm's are running high, around 2,200 while its idoling. After it warms up a little my rpm's begin to fluctuate down to 1,500 rpm's and back up to 2000 rpm's. Once the car is fully warmed after about 4 minutes the rpm's return back down to their normal running level of 1000 when the car is idoling. I'm miles per gallon have also been reduced from about 27 to 21. this could just be because of the fact that the engine is running so high before it warms up. Any idea whats wrong and what I can do to fix it?