ASK THE MECHANIC: What causes internal car damage?

Hello Paul, my Toyota Kluger automatic gearbox leaks oil and does not shift gears. A mechanic has inspected it and advised that it has internal damage so I should get another gearbox. Can I revive the gearbox with a simple oil change? Edward.

Hello Edward, if the transmission oil leak caused damage to the gearbox clutch packs and metallic components (valve body or pump), no amount of oil change will restore normal performance. The oil change should have been done earlier and the leakage stopped on time. Transmission oil (ATF) helps a conventional automatic gearbox to engage gears by hydrostatic pressure. ATF also helps to lubricate moving metallic components, cool them down as well as prevent metal shear and corrosion.
When the ATF oil ages, its protective and performance enhancing role reduces. If this situation continues you most likely will need to replace damaged components or replace the gearbox out rightly. New automatic gearbox repair parts for a complete overhaul and replacement of the valve body are much more costly compared to buying a quality used gearbox imported from Japan. If an inspection of the gearbox after dismantling confirms the severity of damage then you may just replace it.

My car shakes when driving uphill

Hello Paul, My VW Golf shakes when driving uphill or at 50-100kms. My Mechanic has checked the plugs, tie rod ends and driving shaft and they are all okay. Please kindly advise on what could be the problem. Paul

Hello Paul, loss of engine power driving uphill can be caused by low fuel pressure, among other factors. Your mechanic needs to confirm that the actual fuel pressure values are within range of the recommended nominal values. This can be done with a fuel pressure gauge or diagnostic tool providing engine actual values. In case actual values are below normal fuel pressure range, then replace the fuel filter before buying another fuel pump.
Also confirm performance of fuel injectors at each cylinder.
Buildup of deposits and corrosion on fuel injectors will affect the spray pattern of fuel which distorts air fuel ratio. This causes reduced engine performance and efficiency. Using a diagnostic tool, your mechanic will need to monitor the performance of the mass air flow sensor (MAF). This is a critical component in the engine self-adaptation (adjusting fuel supply) to changing conditions (air volume and temperature) such as altitude or speed.
A faulty MAF can fail to help the engine management system to adapt when you are driving uphill, which can lead to power loss or poor performance.

My engine revs whether it is hot or cold

Hello Paul, you recently answered a question about a problem I think I might be having. When the engine of my Toyota Corolla is cold or warm my car engine revs and keeps oscillating in the middle of 0-1 and during that time it shakes a lot. I have taken it to different mechanics but they have all failed to diagnose the problem. What can I do? John

Hello John, erratic idling at cold start and during warm runs or low engine power exhibited by the engine abnormal vibration can be caused by a faulty or dirty idle air control valve, clogged throttle valve or dirty fuel injectors and fuel filter. You need to have your throttle body cleaned, fuel filter replaced and choose Shell gasoline fuels with new Dynaflex technology for fuel system cleaning.
A good ratio of fuel and air is important for an efficient engine run during idling or driving. Buildup of soot in the idle air control valve or throttle valve will affect quality and volume of air intake. This distorts the fuel air ratios and the effects cause erratic engine idling and efficiency. A dirty air filter or leaking air intake hose usually causes this situation. The throttle body and idle air control valve can be dismantled and cleaned. A dirty fuel filter will reduce fuel pressure and affect the fuel pump performance. Replace it if you have not already.
After fuel burn deposit build up on fuel injectors and intake valves will also prevent instantaneous ignition. Fuel injector holes are as tiny as a human hair. Their spray pattern of fuel is critical for atomisation or efficient burning. Clean air intake valves ensure that the fuel air ratio is appropriate for efficient combustion and good engine power.
Use of Shell Fuel Save Unleaded or Shell V-Power fuels with new and more powerful Dynaflex technology will clean and prevent further efficiency robbing deposit build up on critical fuel system components.