THE UNKNOWN IACOCCA By Peter Wyden Morrow. 416 pp. $18.95

LEE IACOCCA has valued himself so highly that you keep looking for the inevitable correction in his stock. There's little doubt of his business success, his instinct about the Mustang's market (even if others originated its design) or his skill at reviving Chrysler. But when Iacocca claims that he could solve the nation's economic ills in six months (in part via protectionist measures) or, after his falling out with the Statue of Liberty Commission, asserts that his firing bordered on being "un-American," it's time someone pricked the bubble. Or at least sought to interpret Iacocca's insecurity and astonishing celebrity as they reflect on the myth the Chrysler chairman so often invokes, the American dream.

Peter Wyden seems to be taking on these psychological and cultural issues at the start of his unauthorized biography, The Unknown Iacocca. The differences between Iacocca the media personality and Iacocca the human being, Wyden says, are "spectacular": he's ruthless, egotistical, thin-skinned, macho, hypochondriacal. Finding out all this, Wyden says with the self-dramatization that mars this book, was "like a child learning there is no Santa Claus."

If only Wyden, a journalist known for his books on war, had stuck to his guns. But no, the biographer falls under Iacocca's great charm.

It's not that Wyden hasn't uncovered a lot of good stuff. There's Iacocca's shabby treatment of William Novak, the writer of his autobiography who got $80,000 in fees on a book that made over $12 million and whose letter to Iacocca gently asking for a piece of the paperback royalties the Chrysler chairman ignored. More disturbing is Iacocca's disdain for safety, especially his dismissal of the benefits of airbags and his rushing of the Pinto without concern for its hazards. Only mildly horrifying are the executive's fondness for limo retinues and plane fleets appropriate to heads of states and the distribution throughout Chrysler of Mobutu-like photos of the boss complete with quotation. And don't overlook his double standard for women employees and his apparent inability to brook the independence of his second wife, from whom he filed for divorce within a year of their wedding.

One reads all this and waits for conclusions. Iacocca's rage for hype might have occasioned a penetrating look at the vulnerability of the media. Or there might be lessons here about the desperate effect that a driving father has on his son, or perhaps about Iacocca's own anxieties about fatherhood (can't the two main events of his Ford career, the fathering of the Mustang and his firing by Henry Ford II, father of the modern company, be thought of as turning on questions of paternity?).

But Wyden is too unsure of his subject to wade into such waters. Laughably, he speaks of Iacocca's "humility," ignoring strong evidence to the contrary (like David Halberstam's full account in The Reckoning of Iacocca's scheming to get on the cover of Time and Newsweek with the Mustang). Also he buys the view that Iacocca is able to take criticism and has a sense of humor about himself, at the same time glossing over his Machiavellianism -- for instance, his willingness 10 years ago to fire Hal Sperlich, now Chrysler's president, one of Detroit's best car men, so that he might stay (briefly) in good graces with Henry Ford, whom he at first fawned over and later heaped with contempt.

Maybe the problem is that Wyden never got an interview with Iacocca. He whines about this; it seems to make him nervous about what information to trust. He quotes from stories about Iacocca with wildly conflicting thrusts and can't resolve the versions; he tells us of "whispers" that shadow Iacocca, but turns out just to be teasing. And though he calls Iacocca's autobiography unreliable, he often uses it as a roadmap for his own account. Indeed, some of the best material in this book comes straight out of Iacocca.

Finally, desperate for a handle, Wyden calls in a group of experts to judge Iacocca's fitness for the presidency. Their comments only leave a reader further adrift.

The biographer simply hasn't made up his mind about Iacocca, and rather than leave his ditherings in early drafts forces them on the reader. For all the talk of Iacocca's Jekyll and Hyde personality, by book's end Wyden considers his subject a "hero" comparable to a De Gaulle or Churchill and concedes that he might well vote for him if he ran for president. The author has managed to exalt Iacocca by faint criticism.

Philip Weiss is a contributing editor of the Columbia Journalism Review.