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Sensing trouble

Question : MY 2003 Proton Wira 1.3 has approximately 80,000km on the clock.

The problem I am facing is that the engine check indicator lights up intermittently after the vehicle has been driven 8-10km.

The vehicle had been sent to my regular mechanic several times. On each occasion, he merely sprayed the air intake with some kind of solvent and charged me sixty dollars.

Apparently, my friends are facing the same problem and we hope that you can help with our predicament.

Answer : THE problem that you and your friends are facing seems to revolve around the air inlet.

Either the air mass flow sensor or the inlet air temperature sensor could be acting up. Both are essential for the electronic fuel injection system to function properly since the rate of air (measured by mass) flowing into the engine deter- mines how much fuel is to be injected.

Unfortunately, there are no fixed service lives for both pieces of equipment and they are liable to failure at any time.

The air mass flow sensor is a particularly sensitive piece of equipment. The latest types utilise a hot wire. A fine wire is kept at a high temperature so it emits ions to the surround of the flow meter. The amount of ions collected by the surround of the flow meter is a measure of the rate of airflow.

Often, modifications by car owners seeking better performance include the use of a free-flow air-filter that has an oiled element. The oil collects on the hot wire, rendering it useless, and the Engine Control Unit (ECU) is fooled into thinking that the flow meter has failed. The same goes for the temperature sensor.

What your mechanic has been doing is cleaning the sensor but, obviously, the solution works for a while but as long as the original cause is not identified and fixed, the problem will return.

Of course, other problems could include a leaking intake system that allows dirt to collect on the above components.

Poor wiring could also result in similar problems and the best thing to do is to have the vehicle hooked up onto a dedicated diagnostic machine that would pin-point exactly which component is at fault.


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