Hi,

Bought a Honda Civic Si manual '98 two months ago from dealership. 3 Days later start having probs - Starts up fine and runs well for first 3 miles or so then once up to running temperature starts suddenly losing power, then starts forward again - this goes on for a mile maybe then it just resolves. Took it back and was told could be water in Distributer cap from power washing of engine block before sale, also tried fuel cleaner and good gas. No apparent effect. Now 2 months later this is becoming more of a problem, before it was only once every few days, and only then briefly but now it's every trip after first 3-4 miles and occurring even when engine has been running for 10 miles+. Went to Honda garage who knew the car with previous owner and they said they replaced fuel filter and distributer cap 5 months ago - evidently last owner couldn't be bothered finding out what was wrong and passed on the problem. Cheers!

Any suggestions for the mechanic to try?

. Check for codes.
. Test/replace igniter and coil--many AutoZone stores will do this for free.
. Check heated oxygen sensor. While on "open loop" it may work okay, but, once the car warms up, it doesn't.
. Ensure spark plugs (NGK only) are in good shape.