Engine misfire is first problem you should fix

Hey there, time traveller!
This article was published 09/06/2006 (7055 days ago), so information in it may no longer be current.

QUESTION — I own a 1996 Escort LX 1.9 automatic. The check engine light is always coming on and registers no codes. The transmission, sometimes when cold, does not shift until engine warms up, yet sometimes works properly. When engine is warm the transmission works as it should and always has smooth shifts.

At times, the car will not idle unless I take it out of gear, and yet it still seems to be missing. Once in a while, after the car has sat for nine hours, it misses non-stop until the engine has warmed up. On these days, I have to take it out of gear and rev it up or it will stall. On one occasion the check engine light came on, and after three blocks started to flash on and off. Ten miles out of the city, the check engine light went off by itself. It also has a strong unburned gas / varnish type of smell.

I have had the head rebuilt, the timing belt and idler bearing replaced. I change the oil and filter every 5,000 km. As this has been going on for almost a year and we have tried pretty well everything we know how to do, I would appreciate any information you could provide. P.S. the crusher is starting to look mighty good by now.

ANSWER — The engine misfire needs to be fixed as a first step. This is causing the stalling, the check engine light to come on, and probably the transmission shifting problem too. The most common cause of misfires are bad spark plugs or bad ignition wires. I would change them. If the misfire still exists, check the output of the ignition coil with a spark tester. A weak ignition coil can cause misfires, and this happens more often when the engine is cold rather than hot. Before replacing a suspect coil, test for voltage at the coil 12-volt power wire with the engine running. If voltage is below 12 volts, you have high resistance in the wire powering the coil and this could cause the problem.

Dirty fuel injectors could create a poor spray pattern that causes a misfire but this usually happens on a warm engine. I would look at the ignition system first. By the way, the flashing check engine light indicates a misfire that could damage the catalytic converter. The car shouldn’t be driven when the light is flashing.

QUESTION — I have an old ’48 Plymouth that has a six-volt system. I was wondering if I can use two six-volt batteries in-line to get 12-volts output for new items and still be able to use the middle connection of the batteries for the six-volt car gauges, etc. Would I have to change the generator to an 12v alternator only? Please advise.

ANSWER — This type of conversion was common back in the ’50s, when the majority of the auto manufacturers changed from six-volt electrical systems to 12-volt systems. To convert the vehicle to 12 volts, installing a 12-volt alternator is the first step. I would look for one of the older GM Delco SI alternators with the internal regulator. They even make a regulator for these units that is self-exciting, meaning the only wire you need to hook to the alternator is the one directly to the battery. This regulator part number has an “se” at the end, and it was typically used in marine applications although many hot-rodders have used it too.

Next, change all the light bulbs to 12 volt bulbs. The starter doesn’t need to be changed, although it will turn fast. It should last for many years if the engine starts without too much cranking. None of the wiring needs to be changed, as six volt wiring was much larger than required for 12-volt systems. The only place you need six volts is to operate the gauges.

Using two six- volt batteries connected in series is one solution. Use the 12-volts for everything but the gauges and tap into the middle connection for six volts for the gauges. The other solution is to use one 12-volt battery and connect a “voltage tap resistor” into the 12-volt wiring to power the gauges. This resistor is often available at electronics parts supply businesses, and has a moveable clamp that can be positioned on the resistor so that six volts is available from the one lead. I am sure there are digital voltage regulators available too, but the old “voltage tap” is cheap and works well. I look forward to seeing your Plymouth on the road again.

Jim Kerr is an experienced mechanic, freelance journalist and member of the Automobile Journalists Association of Canada. You can contact him via e-mail only, below:

kerr.jim@sasktel.net