Are small 4WD cars guzzlers?

I currently own the SE Ltd AE 100, I am kindly seeking your guidance on the four cars SE LTD AE 100 (Kikumi), SE Ltd AE 110 (Kikumi Kumi), G-Touring AE 100 and Fielder. The problem I have heard about the 4WD saloon cars is that they consume a lot of fuel and have a problem with the gear box. Are there Corolla SE Ltd and G touring that use both 2WD and 4WD interchangeably?
Godfrey

Ans. The major difference between the Corolla AE100 and 110 or the G-Touring and Fielder is the fact that they are different generations of the Toyota Corolla each with different engine technology and body or interior styling. Different generations of these cars have incorporated better fuel saving engine technology such as the variable valve timing (vvti) in the Corolla Fielder. The Corolla has different engine sizes such as 1.3, 1.5, 1.8 and 2.0 litre all of which have different fuel economy depending on their sizes.

Some Corollas have full time four wheel drive (4WD). This 4WD Corolla will consume more fuel than the two wheel drive (2WD) Corolla with the same engine size because all four wheels get the same amount of power all the time. This means the 4WD engine has a heavier drive load and hence a higher fuel consumption. The full time 4WD has two gear ranges: high for normal driving and low for difficult terrain or slippery conditions. There are no Toyota Corolla vehicles with part time 4WD where you can engage the transfer case from 4WD to 2WD when you want to disconnect the front drive shaft from engine drive.

The full time 4WD Corollas do not have the 2 high - 2 low or 4 high- 4 low option available on the bigger non full time 4WD Toyota Land Cruisers. Your choice of the full time 4WD option should be influenced by your need for the facility as this should justify the opportunity cost of the slight increase in fuel consumption. Generally speaking, Toyota gearboxes manual or automatic have no major design problem as long as they are serviced with the correct Toyota recommended gearbox oil. Before you inherit a 12 year old used one in the bond you ought to check that it has been well maintained (oil does not smell is not burnt or with dark debris) or carry out the service immediately.

My 1996 Audi A4 has developed a foul smell from the exhaust similar to that of rotten eggs. The engine response is poor and it does not have power when I accelerate. My mechanic has recently replaced the spark plugs, air cleaner and fuel filter but this problem has not been resolved. What in your opinion could be the trouble causer?
Francis Asiimwe

The foul ammonia like smell from your Audi A4 exhaust and the poor engine performance suggest that it has a damaged catalytic converter (CAT). This is a vehicle emissions control device which is made of ceramic material and designed like a honey comb in your exhaust pipe. The CAT converts toxic byproducts of combustion such as carbon monoxide and unburned hydrocarbon or oxides of nitrogen in the exhaust of your internal combustion engine to less toxic substances by way of catalysed chemical reactions.

A catalytic converter relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter. A damaged CAT disintegrates and blocks the passages of the exhaust pipe.

The CAT may fail due to a malfunctioning Oxygen (O2)
sensor, plugged or inoperable fuel injectors, piston blow-by due to worn out rings, leaking cylinder head gasket, broken choke or carburetor float, excessive cranking time, bad exhaust valves, bad spark plugs, repeated incidences of running out of fuel or the use of leaded, adulterated or contaminated fuel. A damaged CAT affects engine performance by preventing prompt response to acceleration and causing unexplained increase of fuel consumption and the typical ammonia like smell in the exhaust. This is a result of the clogged converter causing exhaust back pressure which affects engine burning. Your mechanic cannot see the clog in a catalytic converter (CAT). One way to tell if the CAT is clogged is to remove it and observe a change in engine performance. When a clogged converter is suspected, your mechanic could temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a positive change in performance. A computer diagnosis if available can quickly identify a CAT failure.

I drive a Toyota Premio, is it true that putting the gear into N saves fuel. I do it a lot. How does one tell that their tyre pressure is good even when the pressure looks okay?

Driving your car in neutral gear is called coasting. Whereas coasting downhill may save a little fuel, in the final analysis it wastes fuel and endangers the driver and other road users. This therefore negates the little fuel saving you may anticipate. When you coast downhill, your engine remains in idle so it consumes some fuel to keep the engine running.

When coasting, it is easy to race the engine forgetting that you are in neutral gear or you have to accelerate when you engage the drive gear.Both actions will inadvertently cause a sudden increase of your fuel consumption rendering your fuel saving efforts worthless.

Disengaging the engine from the drivetrain when you engage the neutral gear limits your ability to manoeuvre, accelerate or get additional engine brake assistance in case you need to avoid a sudden road hazard. It is possible to forget you are in neutral and slide the shifter knob into parking mode which could damage your transmission.

You can tell if your tyre pressure is low when you hear your tyres squeal when cornering or feel the suspension collapsing on one side.
However, the most reliable means to determine the correct tyre pressure is the use of a handy tyre pressure gauge or the heavy duty one at a fuel station. Refer to the manufacturer recommended tyre pressure levels indicated on your door pillar or fuel flap.