Automania/Repair & Maintenance

AUTO QUESTIONS AND ANSWERS FOR WEEK 20

by Bob Hagin

Q. I bought a new Cadillac Seville STS with the Northstar engine. Some time later I noticed the motor vibrating slightly at idle. I took it back to the dealer and they told me that the problem was caused by a bad sparkplug, which they replaced. It seemed to run better after then, but eventually the problem returned and continued to get worse as time went by. Because the warranty had expired, I took the car to an auto service center with diagnostic equipment. Diagnostics indicated that there was a problem in the ignition system. They cleaned the fuel injectors, replaced the fuel and air filters as well as the sparkplugs. The car did run better for a while but again the same problem returned. I returned to the center and this time they replaced the spark plug wires. Again the problem appeared. The car seems to run better for a short time but then starts to run roughly again, especially when accelerating or going up a slight grade. C.H. Chesapeake, VA

A. If your problem with a bad sparkplug keeps happening on the a particular cylinder, the technician should concentrate on that area rather than take a shotgun approach and hope to hit the problem. If a single sparkplug goes bad before the rest, it could be fouling out because of too much fuel (faulty injector system) or oil fouling because of a bad valve stem seal or leaking piston ring. It could also be overheating because of a localized vacuum leak - maybe a cracked vacuum hose or leaking gasket. Troubleshooting is about 80 percent observation and 20 percent perspiration.

Q. What can I do about a 1995 Dodge Caravan SE that bottoms out when heavy passengers ride in the second seat? Two years ago I drove 125 miles with such a heavy load it bottomed out at the slightest bump. Some people I've talked to say that I should put heavy-duty shock absorbers on but my limited knowledge says that shocks only keep the vehicle from bouncing. The local Chrysler dealer tells me that there are no overload or heavy-duty springs for this model. A local tire dealer says that I should add a leaf to the springs. G.B. North Highlands, CA

A. Heavy duty shocks would no doubt help since they offer increased resistance to compression and would slow down your van's bump reaction. A more upscale approach to improved shock absorber action would be to install shocks that have an air chamber built into them. To increase the load capacity, the operator applies air pressure to a remote Schrader air valve that the mechanic has installed near the back bumper. Another option is shocks that have an auxiliary "overload" coil spring wrapped around them. These aren't readily available for all vehicles so you'll have to shop around at independent parts stores or at RV supply shops. Installing an extra spring leaf to each side would be my last choice.

Q. I let a friend borrow my 1971 Toyota Corona and she drove it without oil. When I had it towed back to my house, I found that the oil filter was loose. She swears that no one messed with the engine. I've owned it for over three years and never had a problem like that. How would it come loose? Since then I've given it a tune-up but the motor sounds like it's scraping against something. I think I need to replace it but what size motor can I put in it? Right now it has an 8RC. What does that mean? I've seen an older Toyota with an 3RC engine in it. H.V. Springfield, OR

A. The only time I've seen oil filters come off was when they were built wrong and the incorrect thread in the hole shook loose. There are places that supply used engines from Japan but they tell me that the 8RC is too old to be available. Installing a later model Toyota engine would require another transmission and lots of underhood modifications. Your best bet is to rebuild what you have if you want to keep the car.