1998 Honda Accord

Always done scheduled maintenance. Sporadic problem getting engine to fire off. When it finally does it runs rough for about 20 seconds before smoothing out. Won't have the same problem for another 2 weeks or so. Local mechanic says diagnostics look good & can't get car to replicate the problem. No check engine lights are coming on. Exhaust smell is a little strong but mechanic doesn't think catalytic converter is the issue. Wife also says occassionally when she stops at a stop light the engine will start racing for a few seconds & then die. She says she has to turn off A/C & must pump the accelerator hard to get it to fire----runs rough for a few seconds then finally smooths out. Battery checks ok. Mechanic said to quit using gas containing ethanol. Have started using Shell fuel. Told mechanic to put a new fuel filter on. Mechanic says I would have to put a new fuel pump/strainer etc. On and would cost $ 400+. Says he doesn't think that's the problem and recommends that I take car to a Honda dealershp for their special diagnostics equipment.