* Dow down 0.2 pct, S&P 500 off 0.3 pct, Nasdaq off 0.3 pct
* Federal Reserve says to keep buying mortgage debt
* Boeing dips after results, but Dow Chemical jumps on job-cut plans
* Facebook shares jump a day after results
By Caroline Valetkevitch
NEW YORK, Oct 24 (Reuters) - U.S. stocks ended lower for a second day on Wednesday, as investors soured on another round of underwhelming corporate results and the Federal Reserve said it would stick to its stimulus plan until the job market improves.
The S&P 500 has lost 3.6 percent over the past five sessions, hurt by weak earnings outlooks and top-line revenue misses from large multinational companies. The index is now down 3.9 percent from its closing high of 1,465.77 set on Sept. 14.
Boeing bucked the trend with a more optimistic outlook, but it could not break away from the rest of the market as it was pulled into negative territory in the afternoon. Shares of the defense and aerospace company, a Dow component, fell 0.2 percent to $72.71.
The Fed, in its latest policy statement, said it would keep buying $40 billion in mortgage-backed debt per month to keep interest rates low until the job picture gets better.
"Unemployment is staying where it is, new jobs are minimal, and the Fed is staying defensive," said Allan Flader, financial advisor at RBC Wealth Management, in Phoenix. "I would be surprised if they went to a neutral stance any time soon. You need to see more credible increases in employment, and it's just not happening yet."
On Sept. 13, the Fed unveiled a third round of economic stimulus, or quantitative easing, known as QE3.
The Dow Jones industrial average shed 25.19 points, or 0.19 percent, to close at 13,077.34. The Standard & Poor's 500 Index dropped 4.36 points, or 0.31 percent, to 1,408.75. The Nasdaq Composite Index slipped 8.77 points, or 0.29 percent, to end at 2,981.70.
After the close, shares of Best Buy Co slid 6.9 percent to $15.75 after the No. 1 U.S. electonics chain warned that its fiscal third-quarter earnings and same-store sales would fall. Best Buy closed the regular session at $16.92, up 0.3 percent.
But shares of online game maker Zynga jumped 12.7 percent to $2.40 after the bell after the company raised the lower end of its 2012 earnings outlook. In regular trading, Zynga fell 3.2 percent to close at $2.13.
During the regular session, Facebook Inc shares soared 19.1 percent to $23.23 a day after the social networking company's quarterly results showed a surprising surge in mobile advertising revenue.
Shares of Apple, scheduled to report after Thursday's close, rose 0.6 percent to $616.83.
The day's other gainers included Dow Chemical Co, the largest U.S. chemical maker, which said late on Tuesday it would cut 5 percent of its work force and shut 20 plants to counter a slowing global economy. Its stock jumped 4.7 percent to $29.88.
On the down side , shares of movie rental company Netflix tumbled 11.9 percent to $60.12 after it cut its subscriber forecast, and shares of data-storage equipment maker EMC Corp fell 0.9 percent to $24.46 after it cut its full-year outlook.
Eli Lilly and Co and Bristol-Myers Squibb Co posted lower-than-expected profit and their shares fell. Eli Lilly shares tumbled 2.7 percent to $50.50. Shares of Bristol-Myers slipped 0.6 percent to $33.05.
With results in from 186 of the S&P 500 companies, 59.1 percent have reported earnings above analysts' expectations, below the 62 percent long-term average, according to Thomson Reuters data.
For revenue , just 38.2 percent of companies have beaten analysts' expectations, while 61.8 percent have fallen short. In a typical quarter, 62 percent of companies beat estimates.
Homebuilders' stocks ranked among the session's best performers. An index of housing stocks shot up 0.7 percent. Shares of PulteGroup, one of the largest U.S. homebuilders, gained 0.8 percent to $17.45.
Sales of new U.S. single-family homes jumped 5.7 percent in September to the highest level in nearly 2-1/2 years, offering more evidence that the housing market's recovery is improving.
Volume was roughly 6.2 billion shares traded on the New York Stock Exchange, the Nasdaq and the NYSE MKT, compared with the year-to-date average daily closing volume of 6.51 billion.
Decliners outnumbered advancers on the NYSE by a ratio of about 16 to 13. On the Nasdaq, about 14 stocks fell for every 11 that rose.