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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 36
by Bob Hagin
Q. My car is a '91 Buick Skylark V6 with and automatic transmission and 31,000 miles. It was bought in '94, driven about 500 miles and then put in storage for almost four years. I then got it road-ready with new tires, a tune-up, new battery, new fluids and an oil change. It ran fine for two months and then it began to die at stop signs but I could always restart it. My mechanic put fuel dryer in and it was great. I went to Arizona and New Mexico and it worked fine. Then recently it started the same dying routine. My mechanic has now cleaned the throttle plates, checked for fault codes and added more fuel dryer. He now says he doesn't know what is wrong. I drive my Buick two or three days a week.
A. The requirements of a gasoline-powered internal combustion engine are pretty simple: it needs fuel, spark and compression and they all have to be present at the right time. In the case of your Buick, you've got compression or you couldn't restart the car. If the problem was in the electronic ignition system, it might take a while to restart it after something cooled down or reestablished a faulty circuit. Since the problem started after the car sat for several years, I'd bet on the fuel delivery system. You didn't mention the replacement of a fuel filter. Have it changed and check it for being filled with debris. If a car sits a long time with a half-filled gas tank, the water that's in it (up to 3000 parts per million) can affect the material it's made of and shove "whatever" into the fuel filter, carburetor or fuel injection parts. You may have to have the tank pulled and cleaned.
Q. In 1994 I bought a '79 VW camper Type II with an engine installed at 107,000 miles and dual weber carburetors. It currently has 138,000 but the engine backfires even after a recent tune-up whenever I turn off the engine. It happens after a long drive or after a half hour or more when the oil temperature reads 180 degrees or more. My mechanic sold me the van and said it was the result of using dual carburetors because they don't have an automatic fuel shut-off. Apparently the former owner switched to carburetors after the fuel-injected engine died at 106,000 miles. I usually keep the engine running between 180 and 210 degrees depending on the time of day. I also recently had to run it between 230 and 250 degrees for a week but I always let it cool down when I crested a grade. Apparently it was out of tune.
A. It's possible that the engine is running very rich on deceleration and dumping a lot of fuel into the combustion chambers. From there it could go into the exhaust system where it get hot enough to explode when air reaches it from the outside. The best check would be to put it on a dynomometer, hook it up to an infrared analyzer to see if it's running lean, rich or OK at normal road speeds with a normal load on it. Weber carbs are very tunable so check for a high float level, plugged anti- siphon passages or incorrect jetting. Also try a chemical cleaning of the combustion chambers. One of the problems with making a drastic change like going from F.I to carburetors is that you never know if things are just right.
Q. My 1994 VW golf has a stick-shift and 65,000 miles on it. Over the past couple of weeks the engine seems to be getting a bit noisy. The noise doesn't happen until the car is under way and cruising at normal street speeds like 25 to 30 MPH. I took it in to our local gas station but the mechanic there can't find a problem. Is it something simple?
A. I could be something as simple as the need to tighten down the mounting bracket for the steering pressure line mount at the front of the engine but then it could be something more serious. Take it to a VW expert for a more thorough examination.
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