Don’t worry: Car will ignore gear shift at high speed
Question: I recently took a test drive in a 2011 Lexus RX350. Since this car did not have a navigation system, I asked about a backup camera. The guy driving with me indicated that it appeared in the mirror, and proceeded to move the selector from drive to reverse at about 50 km/h. The camera came on and there was no change in the rpm or forward motion.
D.K. Answer: That’s because the engine-management system is smart enough to know that allowing the transmission to engage reverse while moving forward at speed would do the transmission no good at all. The backup camera came on simply because the shift lever was moved to the reverse position.
Hopefully the driver — was he the owner or a salesman? — must have known the transmission wouldn’t engage reverse at speed. He was either trying to impress you with his knowledge, or if he didn’t know, he was a very lucky idiot.
Q: We have a 1993 Chevy Lumina with a 3.1-litre V-6. Every now and then the motor will turn over but not start. We wait a few minutes and it fires right up. This happens after we go some place for an hour or so. Battery cables are clean and tight. I installed new plugs, wires and a new exhaust gas recirculation valve. I brought it to our mechanic but he couldn’t figure it out. Any help would really be appreciated.
C.T. A: The first step is to check for any diagnostic fault codes stored in the powertrain control module. If none are found, think in terms of fuel pressure and spark — an internal-combustion engine cannot start without both of these. Could it be vapour lock, where the ready fuel supply in the fuel rail under the hood is heated to the point that the fuel boils, causing a loss of fuel pressure? Or could it be caused by an overheated ignition module located under the coil packs?
To help the diagnostic process and point your mechanic in the right direction, check for spark with a timing light while cranking the non-starting engine. Also, with a fuel pressure gauge connected to the test port on the fuel rail, run the engine up to full temperature and then monitor fuel pressure bleed-down after shutdown.
If it seems to be a fuel-pressure issue, next time it happens cycle the key on for two seconds, then off. Do this six times, then try starting the engine. If it starts, you’ve confirmed a fuel-pressure issue.
If there’s no spark, try cooling the ignition module by misting the area around the module with a spray bottle of water. If this expedites starting, high underhood temperatures may be the issue.
Q: I have a 2007 PT Cruiser with 37,000 kilometres. I change the oil each year, but nothing else. It’s working fine. What about plugs, transmission, brake fluid, antifreeze, etc.? I am keeping the car. What do you recommend?
P.C. A: Your extraordinarily low annual mileage certainly extends maintenance intervals, but does not eliminate them. Check your owner’s manual. Besides changing oil and filter as you’ve been doing, my ALLDATA automotive database calls for tire rotation every 8,000 kilometres, spark plug and air filter replacement at 50,000 km and a coolant flush at 80,000 km. There is no call for transmission service. I would recommend either bleeding the brakes to exchange old brake fluid for new, or at least siphoning the master cylinder nearly empty and refilling it with fresh brake fluid every two years.
Q: In order to power a few 120-volt items while driving, we are using an inverter plugged into our Mitsubishi Delica’s cigarette-lighter socket. When the car’s running, is the socket and other electronics (lights, radio) powered by the alternator, having little effect on battery life? Or are all the electronics powered directly by the battery, with the alternator simply working to keep the battery charged?
I read that deep-cycle batteries can be run down to about a 50 per cent charge, while normal batteries shouldn’t be allowed to dip below 90 per cent.
What do you think? J.A.
A: A vehicle’s battery is intended to start the engine, provide accessory power — to a point — when the engine isn’t running, and serve as backup if the alternator can’t meet all the needs while the engine is engaged.
When you’re driving, the alternator ought to create all the energy the vehicle needs up to the point of its production limit, which in J.A.’s case is 65 amps. The sum of an engine’s electrical consumption (management, fuel, ignition systems) and the vehicle’s headlights and radio should be about 20-25 amps, leaving a nice reserve before the battery would be called upon to help out.
J.A.’s cigarette lighter-powered inverter (likely 150 watts) might pull as much as 10-15 additional amps of current from the alternator when at full output, resulting in a total pull still within the alternator’s comfort zone.
Larger inverters are sold, but using one might result in popped fuses or smouldering sockets. Hardwiring directly to the battery with short, thick cables is the solution. Before doing that, check the labels on your accessories to determine their wattage.
It’s best to employ an inverter only with the engine running and, yes, to not discharge a battery below certain charge points. Drawing 10 or 15 amps from a typical battery when the engine’s off would drain it to the point of a nostart condition in about three or four hours.
While stationary, using a 100-watt solar panel (they cost about $120 online) could, under optimum conditions, provide 6-7 amps of charging current for the battery. Eight hours of bright sun could compensate for about four hours of inverter use. A charge controller would be needed if you want to use the panel on a continual basis or if you want to use multiple panels.
Motoring note: Thanks to an anonymous reader for this: “I just read the question about how to fix a screechy belt. I had a similar problem and I replaced belts and checked the tension — the usual stuff. My brother suggested that the pulleys might be out of alignment. Sure enough, the mechanic checked and found that one pulley was not in alignment with the others. He made the adjustment and no more screeching.”