Does your vehicle have a shift-up arrow illuminate (in the main Odometer display center) when driving to force you to shift to a higher gear when conditions are more optimal?
Why? Timing and advance. IF you have a lot of miles on it and it's a manual - the system may see a condition so it can't advance the timing to optimize the higher torque needed - so the Knock sensors tell it it cannot find ideal settings, so it "fades" or falls flat - check your knock sensors - see if they need service or replacement - failed knock sensor may generate too much noise so the system thinks it's too far advanced and if reduces or retards, the timing advance to lessen the noise and try to get optimal for the load to mixture setting - you feel this as a fade in performance.
Else dragging brakes or a failing bearing can place a load on the engine aggravating this condition.
Got pulled away, wanted to add in this ...
Even if it's not any sensor issue, does the vehicle have a lot of km (miles) traveled on it?
Thinking Air Filter, Plugs changed, was radiators fins ever been rinsed to remove bugs, salt, dirt - from blocking airflow? Hot engines quickly thin out oil and often have issues with sagging performance. Hesitation can due to worn plugs or the air filter needs service.
- If you don't already know, the engines timing is done in two levels, one; the ignition fires the plugs per the ECM/PCM using sensors to fire the plugs at the right time.
- The second one in timing, uses the motor but to a different degree, it moves the Intake and Exhaust Camshafts to adjust the level of Intake timing (air going in) Compression (Mixing and power) and Exhaust timing (Emission and exhaust volume).
- In earlier times carburetors and vacuum controlled the fuel air mixing and delivered results as feedback to the load on the engine using vacuum from the intake or ported - to advance timing to mechanically move the rotor/points and condensor in the distributor cap to advance power and speed delivery. Now it's Fuel injection and to a point; the feedback-principle vacuum provided in the earlier days is now being used but with oil as the method to adjust the timing by affecting the volume of air and how it moves in and out of the motor by changing the way valves open and close. The rotor is now the camshafts and by using oil, by volume and pressure - to affect the amount of air/fuel charge is present in the cylinder.
IF so - and you can get it's oil changed, this may help you in diagnosing the condition of either; sensors going bad, or you just have a worn motor and it needs some service.
Changing the air cleaner to a new one and the oil and it's filter to a higher viscosity range can offset bad or worn plumbing where the oil flows thru the ports and channels, but it cannot build up enough volume or pressures due to the worn journals, bearings and camshaft ports. The added volume of air can help build compression to restore performance
- Remember I mentioned the Shift-up arrow (or light)? - even a dirty MAF sensor in the snorkel and the Intake manifold MAPT sensor plugged or fouled with oil, can change the way it runs because the engine is trying to keep emissions under control - and can affect the sensors in telling you when it's time or it thinks it's time, to shift to another gear.
Since it's going into summer here, I change my own oil from summer to winter and back to summer...My car has 1.6L N/A L4
- Winter; I use a blend of 3 Quarts (not Liters) of 5W-20 - and 1 Quart (not Liters) of 0W-20
- Due to my local winter season conditions in Michigan - temps often drop below 20F and vehicle gets parked outside
- Summer; I use 4 Quarts (Not Liters) of 5W-30
- Type of Oil Blend, Synthetic, Synthetic Blend, or Natural - make sure it (and it's SAE rating) meets your engines needs per your owners manual.
- You are not required to stick with an oil blend that is too thin or is unable to keep the vehicle properly protected when driving in extreme conditions - you can damage the engine if your oil levels or viscosity is unable to provide protection during operation. Especially in High-Mileage vehicles.
- Oil in USA uses Quarts for measurement as in volume and capacity standard
- - Liters are standard in the EU/UK region so you will need 3.7L for it's capacity - overfilling the crankcase with oil will damage the motor
- PLEASE Check your Owners Manual first for capacity guidance.
Some simpler maintenance may help with the hesitation issue, and should be checked for first and done right away if it hasn't been done in a while to see if it helps - else you may need to take it in for service.
