Automania/Repair & Maintenance

AUTO QUESTIONS AND ANSWERS FOR WEEK 42

by Bob Hagin

Q. My 1991 Oldsmobile Bravada would not pass the state emissions test. I had a local Oldsmobile dealership tuned it up and replaced the spark plug wires, the thermostat and the oxygen sensor. Still it did not pass and I had to take a voucher instead of having it pass. The people at the emissions station said that my gasoline is supposed to be burned twice and it is only being burned once. The dealership shop says that everything else checks out fine. My gasoline mileage is pitiful compared to what it used to be J.H. Joliet, IL

I think you needed to see a trouble-shooter rather than a parts changer. When a vehicle doesn't pass a state-mandated pollution control inspection, the fault can be in several different areas and caused by a variety of maladjustments or mechanical problems. The emissions that traditionally have to be controlled at the field level are hydrocarbons (HC) and carbon monoxide (CO). Oxides of nitrogen (NOx) are also a factor but they can't be measured without the use of very sophisticated equipment and usually this is required in areas that have unusually high concentrations of air pollution. Faulty plug wires and oxygen sensors are only a few of the items that control emissions. Have a technician check out your Bravada's various systems. Don't simply tell him or her that you want a tune up. Be very specific and tell the shop that you want it to pass the emissions control test. To do it completely, the shop will need a five-gas analyzer and a dynomometer but sometimes finding a shop with this kind of equipment is difficult and even impossible in some areas.

We have a 1992 Toyota Previa van with all-wheel-drive that we use a lot on kayak trips and to get into out-of-the-way camping areas. The only problem that we have been having is that the engine seems to be leaking motor oil. When we shut it off, we get the smell of burning oil coming out from under the engine area. We took it to a dealer to check it but the manager said that there was a problem that his mechanics couldn't pinpoint without taking things apart. He then said that he couldn't give me an estimate until they got it apart. Is this a common problem with Previas and can't an oil leak be found without taking the engine apart? S.A. Richmond, CA

Although it's not totally rare for the Previa to leak motor oil, it's not common. The four-cylinder engine in you van lays on its side and it's quite an ordeal to check the oil level in the engine. It has a oil holding reservoir with a device that automatically tops up the engine oil level when it goes down. Toyota technicians tell me that they've come across Previas that leak oil from the oil pan, the valve cover gasket and from a couple of other non-pressurized areas. The best system to use is to put the van on a lift, thoroughly clean the underside of residue oil, put a special ultraviolet dye in with the oil and then run the engine while the van is still on the lift. The technician then examines the underside of the engine with an ultraviolet light and the leaking oil shows up slightly yellow. From there, it might be an easy or a hard "fix" but at least the mechanic knows where the oil is coming from. This is a pretty fool-proof system but in one case, they still haven't been able to find the culprit.

Is there a definitive book on automobiles rather than those glossy coffee-table books? My husband is interested in the history of makes and says he's bored with "fluffy" stuff in most auto books. L.C. San Antonio, TX.A

A. I use "The New Encyclopedia of Motorcars - 1885 to the Present" by G.N. Georgano, published by E.P. Dutton, New York. It's hard to find but even used, it's great. Mine is the third edition dated 1982.