Is my mechanic right to refer me to a dealer for diagnostics and repairs?

Dear Car Talk

Dear Car Talk | Nov 01, 1993

Dear Tom and Ray:

I have a 1985 non-turbo Chrysler LeBaron snazzy red Convertible with 154,000 miles on it. I recently took it in for a tuneup at Sears. Both before and after, the engine idled roughly when I was in gear, say, at a red light. I took it back to the mechanic who looked it over and wrote "Engine is set to specs; Appears to have problem in computer engine control system; Has vacuum leak at the air cleaner hot air diaphragm." And then, the best part: "There are 19 cold drivability tests and 21 warm drivability tests that have to be run to find the cause for excessive fuel from carb. Recommend dealer for computer diagnosis." Do I have to go to the dealer and get all of these tests?

TOM: There are two possible reasons he told you to go to the dealer, Daniel. One is that he doesn't have the equipment necessary to do the computer diagnosis. It requires a digital readout box, and a lot of shops don't have them.

RAY: The other possibility is that he has no idea what he's doing, or isn't particularly interested in solving your problem. Before I sent you to a dealer to pay for a digital readout, there are a couple of simple things I'd do. First, I'd fix that vacuum leak he mentions. That could cause excessive fuel consumption and rough idling.

TOM: But even before that, I'd do a compression test to see if the engine is basically sound. At 154,000 miles, one of the valves could easily be burned. And that certainly would cause rough idling.

RAY: If you run into a dead end after that, then you can make an appointment with the dealer for a computer diagnosis. But I think you were getting the old brush-off, Daniel. And you don't need a computer diagnosis to tell you that.

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