Ask the mechanic >Why can’t I shift gears easily?

I appreciate your continuous publications every week about cars, it has helped me have broader knowledge about cars and its parts as well as recommended fuel.
I own a Toyota Corona, commonly known as Kibiina, UAK series automatic transmission in perfect condition.
But lately, it has been having a problem in shifting gears. When I engage gear on ‘D’, the takeoff pick is either slow which I suspect it could have picked from gear 2, or it at times picks with full force assumed to have picked from gear 1 and as I drive along, it has normal shifts of gears even, over drive button is okay.
I gave it a trial recently when I went for a graduation at Gulu University and it was perfect on the road. Please help, I also need to know if driving it like that could be risking my gear box?
Lee, Arua

Lee, the symptoms you describe suggest that your Toyota Corona transmission is malfunctioning and you need a good mechanic to inspect and confirm its status. Automatic transmission performance can be affected by the transmission fluid quality and quantity; transmission electronics (electro hydraulic control unit - valve body) and the engine performance, particularly the throttle potentiometer. Automatic Transmission Fluid (ATF) provides the viscous pressure and lubrication essential to operate the automatic gearbox.
Therefore, maintaining the manufacturer recommended quality and quantity is important. ATF should be changed periodically with the correct specification indicated on the dipstick (DEXRON II / TOYOTA TIV), especially when it changes from a bright red colour to a brownish or dark colour and has a pungent smell. During the ATF inspection, should the mechanic detect that the oil smells burnt, then it should be examined closely to establish whether there is burnt debris from damaged gear clutch material. Should the ATF fluid condition be fine, with no leaking points to affect quantity, then ask your mechanic to check the valve body and transmission control electrics which help to allocate ATF to the correct gear clutch pack 1-4 or reverse.
The mechanic will decide whether he needs a car electrician or computer diagnosis to rule out valve body failure. Should the gearbox inspection findings determine that it is okay, then the mechanic should check the engine performance. Particular attention should be to the throttle potentiometer which may need cleaning to remove carbon deposits from the throttle valve. I hope you have replaced your canister fuel filter located in the engine bay as this can also affect engine performance.

Thanks Mechanic for answering my questions about 2 and L on my automatic transmission. Now I also find most Subarus with 3. What is it for and talk about D4 cars as well.
Ronny Paul Kaweesa

Mr Kaweesa, some vehicles built after 2000 come with 4 speed automatic transmissions. On these transmissions, you can select position 3 for the automatic gearbox to shift only up to three gears, especially when driving on a hilly road stretch or when towing another car or trailer. This prevents automatic transmission damage by over shifting upwards and backwards.
The Toyota D4 engine is a current stage in the evolution of car engine fuel delivery systems from the ancient mechanical carburretor, simple Electronic Fuel Injection (EFi) to the Direct Injection in four cylinders. Mitsubishi call it Gasoline Direct injection (GDi); Mercedes call it Stratified Charge gasoline injection (CGi); Volkswagen call it Fuel Stratified Injection (FSI) and Toyota call it Direct four injection (D4). This technology uses an engine computer controlled system to electronically synchronise delivery of the fuel and spark in a manner that enhances performance and fuel economy in petrol engines.
In the D4 engine, fuel is injected under very high pressure into the combustion chamber itself (direct injection) avoiding inefficiencies caused by routing the fuel through the inlet manifold as earlier EFi systems do.
During the combustion process, air is compressed and at a very precise moment fuel is injected directly into the combustion chamber. This allows the engine to produce less emissions while enhancing performance and fuel economy.
D4 engines are very intolerant to deposit build up on intake valves caused by petrol fuel after burn.
Toyota recommends fueling D4 engines with unleaded petrol which is blended with detergent additives to clean and protect the intake valves. In addition to using engine lubricants with detergent and anti sludge additives, the D4 engine spark plugs, air and fuel filters should be monitored and replaced periodically.

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