TORQUE SHOP #3

This issue’s thematic Q&A session is about engine ignition and a misfiring motor.

This issue’s thematic Q&A session is about engine ignition and a misfiring motor.

"SLOW CRANKING IS USUALLY ATTRIBUTABLE TO A WORN STARTER MOTOR."

I am driving a nine-year-old Toyota Corolla Altis. I send my car for servicing every 10,000km at Borneo Motors.

Lately, when I crank the motor to start, I find it rather difficult to get it started. I have to use full force with both my hands to start the engine.

The mechanics at Borneo Motors could not find any fault with the system. They lubricated the keyhole, but after a day, the problem came back. What could be the cause of this problem?

From your description, it appears that the problem is with the ignition key switch itself.

This unit, which is at the steering column where you insert the key, incorporates electrical contacts for various functions, including main ignition, starter relay and also the steering lock.

Difficulty in its operation occurs when an internal part of the switch assembly has worn down or chipped off. This will cause interference between the housing, which is fixed, and the rotating core, which is where you insert the key.

Lubricating using light oil or WD-40 will only alleviate the problem in the short term.

The ignition switch assembly, unfortunately, is not something that can be disassembled and serviced. So the only recourse is to replace the whole unit.

Once replaced, however, it will not be possible to use the existing ignition key. Hence you will end up with two keys – one for the ignition and the existing one to unlock your car’s doors, glovebox and boot.

Also, with some makes of cars, you can have the whole set of locks replaced so that you will have just one key. Your dealer should be able to tell you if this is possible and how much it will cost.

I recently renewed the certificate of entitlement on my car. It has been reliable except that lately, the cranking during startup is very slow. I replaced the battery, which was about a year old. Despite that, the cranking improved only a little initially. What could be the problem?

Slow cranking is usually attributable to a worn starter motor. If this has never been replaced, you might want to consider doing so, as it could eventually fail and not crank at all.

There are, however, wiring issues that could also cause slow cranking. Old wiring in some cars has a tendency to drop in current-carrying capacity. The reason is that the multiple copper strands in the insulated wires can break with age.

Unfortunately, there is no easy way of determining which wire is affected. So the best solution is to replace the complete set, including the earth-link between battery and engine.

Bear in mind that prolonged use of such weakened wires can cause heat build-up in the wiring loom that can lead to breakage in the insulation.

My car, which has just passed its three-year warranty period, jerks rhythmically for several seconds every time I accelerate, especially from a low speed.

I do not experience this while I am on the move and cruising, or when I accelerate gently. The jerking begins again if I want quick acceleration.

I had the car serviced and the spark plugs replaced. There has been a slight improvement, but the jerking still occurs. I am worried that this could be a serious and costly engine problem.

The symptoms you describe appear to be caused by an ignition malfunction. This is commonly known as “misfire”.

You did the right thing by replacing the spark plugs but, as you say, the problem persists, so your next course of action is to focus on the ignition components.

For systems with remotely located ignition modules, the cables leading to the spark plugs should be replaced first as they are relatively inexpensive.

Many cars today have individual – meaning one for each spark plug – ignition modules or coil-packs. In this case, the electronic diagnosis would reveal the faulty ignition coil.

But it would be advisable to consider replacing all the individual units instead of just the faulty one. The fact that one is already about to fail suggests the possibility that it has reached the end of its lifespan.

In any case, the car will perform noticeably better if all the ignition coils or modules are replaced. This is not a serious or costly problem as long as you fix it soon.