Whenever Terry Markin started his 2000 Audi A6 in June, it was deja vu all over again. The engine would get noisy for a minute, then quiet down. Same thing had happened last January, and once before that.

Both of those times, Audi of Alexandria replaced the secondary air-injection pump. No charge. The repairs were covered by a one-year parts warranty.

But the third time wasn't a charm. "They said they would not honor the warranty because water had gotten inside it," says Markin, a Montgomery County resident. "When I said I didn't know how, they said that perhaps there was a heavy rain!"

Markin said he couldn't believe a summer cloudburst could drive water inside a sealed air pump under the hood. "They suggested I drove through a river," he says in disbelief.

Bad enough that the dealership kept his car a month waiting for replacement parts. Then it charged him $3,122 -- about a third of that for a 60,000-mile service.

"I assume that they told me the truth [about] water in the air pump. But I have a suspicion the pump may not have been sealed properly," he said. "I'd be happy if they just honored the warranty. . . . Now I fear that I may have to pay to replace it repeatedly."

Car repairs are tricky business for consumers. Most of us know so little about cars that we're at the mercy of $100-an-hour mechanics -- whose profession, fairly or not, wouldn't rank high on a consumer trust index, if there were one. So when a service manager phones to say your oil change is done but you need new brakes and the radiator needs flushing, you can't help but feel that the $29.95 oil change just overheated into a $695 rip-off.

Car repairs are consistently among the top three or four gripes in consumer surveys. Auto repairs -- faulty repairs, cost overruns and unnecessary repairs -- ranked third behind home-improvement and car-dealer problems this year in an analysis of more than 400,000 complaints conducted by the National Association of Consumer Agency Administrators and the Consumer Federation of America, a District-based coalition of 300 consumer groups.

Thomas McLaughlin said it's no wonder most motorists are intimidated. "It's a very technical subject. Few people are that astute to know how to discuss it," said McLaughlin, manager of the American Automobile Association's Mid-Atlantic Approved Auto Repair Program. Often, he added, repair-shop diagnoses sound "like they are making up words just to take your money."

That's how Markin felt. He telephoned the customer advocate number at Audi of America headquarters in Auburn Hills, Mich., an idea that sputtered like an engine out of tune. "They merely put me on hold while they called the local dealer who serviced my car," he said. "When they got back on, they told me what the dealer had said."

Left with no recourse, Markin contacted the Consummate Consumer, who hadn't gotten his hands greasy on a good car-repair dispute in many a mile. Hey, looking under the hood of car-repair problems isn't much fun.

Turns out there was water in the air pump, but it wasn't Terry Markin's fault. Audi spokesman Patrick Hespen said that when Audi sent a "field representative" to investigate the dispute, he found that the previous pump repair didn't replace auxiliary parts -- which had to be purchased separately. As a result, exhaust got inside the pump, causing condensation.

"The dealer was mistaken and it should have been warranteed. Audi has directed the dealership to refund the customer his money," said Hespen, adding that to prevent similar problems Audi has changed its air-pump kit to include auxiliary parts.

Happy ending, right? Not quite. Martin received a refund check for $979.55 -- not the $2,000-plus he thought he was charged for the air-pump job. Hespen says Audi calculated that the warranteed air pump and labor totaled $979.55. The rest of the bill covered other repairs. Markin says other than the 60,000-mile service, he didn't ask for other repairs.

Markin is also peeved Audi sent him a check with no apology, no explanation, no best wishes. "Audi still does not appear to be fully owning up to its responsibility," he said. "I fear the problem here may be larger than simply one guy and his air pump."

AAA's McLaughlin says it could be -- which is why AAA's Approved Auto Repair Program may save consumers some grief by steering them to AAA-certified shops that are mechanically competent and whose business ethics, AAA says, are tight as air-gunned lug nuts. AAA does on-site inspections and surveys 250 to 300 of each shop's current customers.

Non-members can use the program online to locate approved mechanics, but AAA members who take their cars to approved shops get a 12-month, 12,000-mile warranty on repairs, discount coupons and free dispute resolution. "If we decide in favor of the member, the shop has agreed to do whatever our decision is," McLaughlin said.

"People are looking more carefully at their driving budgets because of the gas prices," he adds, "but [car repairs] come down to trust and reputation."

Car Donation Addendum

The recent column about restrictive new tax deduction rules for car donations ("Car Rules Drive Donors Away," Nov. 6) focused on the vast majority of donated cars -- those that go to charities that sell them to fund their missions.

But there's an exception: The Internal Revenue Service continues to allow consumers to claim fair-market value on donated cars that charities don't sell but instead use "to further their charitable mission," such as giving the car to a disadvantaged family. Organizations such as the Car Ministry and Charity Cars depend on getting vehicles to give to the needy.

But a warning: These charities often require higher standards for cars they accept. Sometimes they don't determine whether a car meets the criteria until it's donated. Cars not up to snuff are sold -- and then the donor can deduct only the selling price.

If your donated car is used charitably, you determine its fair-market value. The IRS defines that as the price a willing buyer and a willing seller would agree on. Go figure -- but figure on the tax man paying you a visit if you inflate it.

Got questions or comments? A consumer complaint? A helpful tip? E-mail details to consumer@washpost.com or write to Don Oldenburg, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Because of the volume of mail, personal replies are not always possible.