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Automania/Repair & Maintenance
AUTO QUESTIONS AND ANSWERS FOR WEEK 23
by Bob Hagin
Q. I have a 1985 Toyota Camry. When I was entering the freeway going uphill on the on-ramp and I stepped on the gas pedal to downshift, the car slowed and nearly stopped. I shifted to neutral, then jazzed the gas pedal to increase the RPM. I shifted back into drive and then the car was OK. This has happened five or six times in the past two years. Once the engine stopped completely and had to be restarted. Is the problem vapor lock? What can I do to cure it?
A. Since the problem only occurs sporadically (six times in two years isn't really very often) it's going to be tough to do any as-it-happens testing of the various systems. You don't say how many miles is on your Toyota or if you've had regular maintenance performed on it but after 14 years, it has to be getting up around 150,000 miles if you're an average driver. As a vehicle gets older, it needs more maintenance rather than less. Preventative medicine is cheaper in the long run than surgery and that applies to vehicles as well as people. If you haven't done anything so far to cure the problem, try putting on a new fuel filter. If it doesn't appear overly restricted, your next step would be to take it to a reliable mechanic to have some diagnostics done. Off hand, it sounds like your car has a fuel delivery problem. The scenario as you describe it is that you're going up hill at a relatively low road speed, then stepping on the gas pedal hard to go into an accelerating downshift mode and the engine flattens out. Have the fuel pump pressure and delivery volume checked in the shop and maybe even on the road. It may even be something as simple as a restricted fuel tank filler cap. These can be blown out with compressed air.
Q. I have a 1985 Ford Bronco II with a V6 engine. Recently it lost half of its master cylinder and I got braking on the bottom half of the pedal only. At the same time, I was getting hard shifting from the automatic transmission, especially on the downshift at 15 MPH. After my mechanic installed a new master cylinder, the shifting was a lot smoother but still abnormally rough. Also there's a new sound to be heard. It is either a high-pitched hum or a low-pitched whistle. I am wondering if something could have happened along with the installation of the master cylinder that would have caused a loss of vacuum.
A. The only thing that I know of on an automatic transmission that uses engine (manifold) vacuum to operate is the modulator valve which softens the downshifting at moderate decelerating road speeds. If the diaphragm ruptures the downshifts will be hard. On some vehicles, when the diaphragm ruptures or develops a pin-hole, the engine will slowly suck the ATF out of the automatic transmission and burn it in the combustion chambers. If you haven't had the automatic transmission serviced for a while, this is a good time to have it done. Have the tech check the vacuum modulator valve while the vehicle is up in the air.
Q. We own a 1987 Buick Skylark coupe with a 2.3 liter four-cylinder engine. We bought it about a year ago because it has very low mileage and had been taken care of. Six months later, a rattle started coming from the front of the engine. About the same time, the engine temperature started to go higher than normal. The noise is now louder and the temperature is getting higher. We only use it as a second car.
A. The engine in your Skylark is called the Quad 4 and it's had more than its share of problems. For whatever reason, some of those engines got through without a lubrication hole in the timing chain idler sprocket which also operates the water pump. The fix is to pull the timing chain cover and replace the sprocket, bearing and water pump. Hopefully, the overheating hasn't damaged the head gasket or the head.
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