By Barbara Kollmeyer, MarketWatch

MADRID (MarketWatch) -- U.S. stock futures largely stuck to the flat line on Wednesday, ahead of a busy lineup of data that includes the latest on private-sector employment, readings on manufacturing, and car-sales numbers.

Futures for the Dow Jones Industrial Average (DJZ4) inched up 5 points to 16,970, while those for the S&P 500 index (SPZ4) added 0.2 point to 1,965.70. Futures for the Nasdaq-100 index (NDZ4) slipped 2 points to 4,042.75.

Wall Street stocks on Tuesday limped through the last day of trading for the month and third quarter after a mixed bag of economic data. The S&P 500 index (SPX) eased 0.3% to 1,979.29.

An appreciating dollar (USDJPY) could propel U.S. stocks to fresh gains, a report in The Wall Street Journal forecast. Investors will be looking to gear themselves toward companies that could benefit from a stronger dollar, such as consumer-focused companies like airlines or retailers, Scott Migliori, chief investment officer for U.S. stocks at Allianz Global Investors, told the WSJ.

The dollar (USDJPY) tapped the 110-yen level for the first time since 2008 in Asia, after weak retail sales in Australia pushed that country's currency lower against the dollar, causing a ripple effect and the dollar/yen jump.

Eyes on ADP, manufacturing: Data could provide some direction for traders. Heading up a busy data day, private-sector payrolls are due at at 8:15 a.m. Eastern Time from Automatic Data Processing. ADP is expected to report employers added 209,000 jobs in September. Economists will use this data to get a feel for Friday's nonfarm-payrolls report, where expectations are for a gain of 220,000 jobs.

At 9:45 a.m. Eastern Time, research firm Markit will deliver its manufacturing index for September, followed at 10 a.m. by the Institute for Supply Management's reading for the month. Economists aren't expecting robust readings from either report.

Data on construction spending for August is scheduled for publication at 10 a.m. Eastern Time.

Autos and biotechs: Auto makers will report car and truck sales throughout the day. Expectations are for sales to slow to an annual 16.5 million last month, from 17.5 million in August.

Family Dollar Stores Inc. (FDO) will report earnings ahead of the bell.

Tekmira Pharmaceuticals Corp. (TKMR) surged 27% late Tuesday after the Centers for Disease Control and Prevention confirmed the first known Ebola case diagnosed in the U.S.

Other companies working on treatments for the deadly virus were also active in late trade: Newlink Genetics Corp. (NLNK) surged 13%, Sarepta Therapeutics Inc. (SRPT) rose 7%, and GlaxoSmithKline PLC (GSK) rose over 1%.

Other markets: Oil prices(CLX4) staged a moderate recovery, after a selloff on Tuesday that pushed prices to the lowest in more than a year. Gold prices(GCZ4) drifted lower, with platinum (PLV4) especially hard hit.

Supermarkets were under pressure on the FTSE 100 after sales fell at Sainsbury PLC and U.K. regulators announced a probe into Tesco PLC over its accounting practices. The Stoxx Europe 600 index was flat.

The Nikkei 225 index eased, while Hong Kong and Chinese markets were closed for a holiday. Pro-democracy rallies spread further across Hong Kong on Wednesday, which had some worried about an out-of-control escalation.

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