1992 Honda Accord Ex 2 door 150,000 miles On occassion, but not very often my car won't start whether it is hot or cold. Everything sound good, lights and radio all work, engine cranks but won't start unless I step on the gas (at least that's what I did when I got it going). I have noticed that the rpms at a stop dips to about 500 and when I drive at 70 mph the rpms are at 3000 and all of the sudden dips to about 2700 and goes back to 3000 (kind of like if I take my foot off the gas but I haven't). I have tried a fuel injection cleaner additive, but the problem still happened after that. The Honda dealer wanted to put a $500 alternator in and I said no thanks. Your opinions are greatly appreciated.

About a year after I purchased this car from my sister (only 39k) the car began intermittent valve pinging. I have used every grade and brand of gas and it runs the best on Sunoco 92 grade. I'm frustrated though because it never used to have this problem. I'm running with Mobil 1 full synthetic 5W-30 in the crank. No engine fault codes (like oxy sensors) or anything are indicating. Other than my timing belt having jumped a tooth, am I overlooking something simpler? Thanks