What's wrong with the auto-repair business--and how to go about getting satisfactory, less exorbitant service. Glickman, a former Wall Street Journal staffer, has a bulging file of horror stories--including several about one-fault vehicles that investigators took to be repaired: invariably, all but a few of the shops failed to diagnose the real malfunction and charged for unnecessary work. Among the worst offenders, Glickman reports, are captive outlets run by the likes of J. C. Penney and Sears, along with semi-independent stations franchised by major oil or tire companies (which, in case of disputes, can always disclaim responsibility). Why does a 20-minute chore show up on a customer's bill as a two-hour project? Venality is encouraged, Glickman points out, by a piecework system that pegs most mechanics' pay to time billed--on the basis of generous guidelines in fiat-rate manuals. Manufacturers' time allowances, on the other hand, are penurious: it's more profitable to take a commission from the sale of factory parts. Detroit is also scored for shortstopping supplies of simple, low-cost components, which forces motorists to purchase more expensive subassemblies, and for designing cars without taking maintenance problems into account. Also cited: insurance companies' insistence on so-called preferred body shops--that specialize in beating the clock--to handle collision repairs; abuse of mechanics'-lien laws permitting seizure of cars pending settlement of bills; and a dearth of skilled labor throughout the industry. To protect themselves, motorists should patronize independent diagnostic centers (not affiliated with repair facilities) and, in their absence, do business with approved garages that agree to let the AAA, BBB, or other disinterested outfits arbitrate all disputes. With advice for seam victims and appended listings of relevant public and private agencies, a point-by-point indictment--with practical means of redress.