Automania/Repair and Maintenance

AUTO QUESTIONS AND ANSWERS FOR WEEK 13

by Bob Hagin

Q. I currently own a 1970 Chevrolet Impala convertible. It has the factory RPO LS4 454 cubic inch engine and is fully equipped with air conditioning, power steering and brakes, tilt steering wheel, etc. I'm told that Chevrolet only made 9562 Impala convertibles in '70 and I wonder how many of these had the 454 engine option and how many of these were fully optioned like mine. I believe that most Chevy convertibles of that time didn't have a/c and that most 454's weren't optioned out. I've also been told that 1970 was the last year a 454 was available in the Impala but was available in low compression form in the '71 Monte Carlo. Is there any way to determine a current ballpark value on this car? The CPI doesn't add for big block options and the Price Guide shows a 35 percent increase for the 454 but doesn't list anything for the options that I consider rare. R.D. Pleasant Hill, CA

A. Not all old cars have collectible value and to establish the worth of any vintage machine, an owner should consult one of the many specialized appraisers that are available around the country. The world of collectible or investment-value cars is a lot like the stock market. It rises and falls on the whims of high-rolling traders and yesterday's million-dollar Ferrari may drop by 50 percent in a year. The market is also subject to manipulation by speculators. The true value of any collectible car is what a buyer who doesn't need buy will pay a seller who doesn't need to sell and that's a tough combination to find. A ballpark figure for your car is around $12,000 as far as I can tell since there's no way to itemize the worth of each option.

Q. I have an '89 Ford Thunderbird SC. While driving at highway speeds, it will intermittently buck and start shaking. It happens most often when I'm cruising between 30 and 45 MPH but when I put the gear selector into neutral, it doesn't stop the engine oscillations. The tachometer jumps up and down over a narrow range of speeds but speeding up or slowing down doesn't help. The problem gradually disappears after a minute or so and then everything is back to normal. Only once did it continue after I came to a stop. It has never misbehaved in the shop and the computer doesn't indicate anything amiss. None of the service managers have a clue as to what's wrong. G.B. Norfolk, VA

A. A shop analyzer doesn't always give the answer to a problem and you have to simply try different things. I'd look for an intermittent fuel problem, maybe a partially plugged fuel filter or water in the gas tank. The problem could also be overheated spark plugs that are worn out or the wrong heat range. Your mechanic should also check for a possible vacuum leak caused by a cracked hose or connector under the hood. Troubleshooting engine problems is as much an art form as it a mechanical skill.

Q. We own a 1991 Dodge Caravan minivan that has a little over 80,000 miles on it. It has a V6 engine and we've been pretty well pleased with it but recently it has begun to make a squeaking sound. This happens only when we start the engine or shut it off - never while it's driving along. Sometimes it makes a hissing sound when it is going up hill or accelerating hard. None of the noises are very loud and I hate to take it in for such a minor problem. D.K. Grand Rapids, MI

A. It sounds like there is a problem with the exhaust system around the connector flange and should be fixed immediately. The hissing sound on acceleration is probably a small exhaust leak and the squeaking sound is most likely the exhaust pipe flange moving around on its seat. Any amount of carbon monoxide leaking into the interior of the car is dangerous. Even a small amount can make you drowsy.