[tech487]

Hello, I own a facelifted 3-cyclinder 118i with ZF auto transmission that has about 15k kilometers. It can be considered pretty new. There is a minor inconvenience since I have bought the car. When I press the accelerator gently (without bottoming out) I feel a bit jittery/stuttery sensation. The feeling is more pronounced when I drive in sports mode. It feels like the car jumpy and is moving back and forth very quickly. It's generally ok when kicking down the gas. The RPM gauge looks normal, no sudden ups or downs. Is this a characteristic of this engine/transmission/suspension/runflat tires/rwd etc? Dealership says it's not a big deal because of 3-cyclinder design but I have some doubts. Anyone experienced this? I'm new to RWD cars and 3-cyclinder engines. I can't make sure if anything is wrong or not.

[ovekvam]

No, the car is supposed to be smooth, and not behave like that. Something is wrong.

Compared to engines with more cylinders, the 3 cylinder will vibrate a bit below 1500 RPM under high load, but I guess you will need a manual gearbox to experience that.

[No one]

It's most typical for an (underpowered, petrol?) engine to shudder under high load at low revs.

Regarding the transmission, an automatic should be smooth, but it's not necessary : I recall a typical shudder issue of shifting between the first and second gear ("back and forth") in traffic jams reported for this car (pre-LCI?, 1 Series, second generation).

Regarding the driving mode, I don't remember why (probably ovekvam reported his research on this subject ), but I reckon there's not a linear mapping (well, that's even obvious: modes must vary ) and the Sport mode could "suspend" power output for more of a "burst" when the pedal gets floored.

So, there's probably something wrong but not severely. There's an opinion that keeping the engine at low revs all the time might clog the injection (or something like that) so high revving time after time (at operating engine temperature and not for too long) is good for the engine, cleans it up and might fix minor issues (catalytic converter related in particular).

[ovekvam]

Did the dealership check for stored fault codes from the car? A modern engine should notice and report issues like these.

[tech487]

There are not any faults as far as I know. Next maintenance is nearing, I'd better get it checked out when I'm at it.