Possible causes of car engine hesitating on acceleration.

Belenus

BMW 116i second generation Series1 F20, 1.6 turbo engine, petrol, 6 speed manual. January 2015 so now over nine years old. 36,000 miles.

We bought it almost new with only 230 miles so we know how it has been driven and treated for almost all its life. It has been regularly serviced by BMW for the first five years and since then by a reliable local company. It was last serviced in January 2023 and, according to the on board computer, is not due another service until later this year or a lot more miles.

It mainly does short trips of a few miles with the occasional longer run. I am aware that frequent short trips are not ideal.

Last week we went on holiday in it. On a 160 mile drive on mainly motorways at a steady 70 mph it was as smooth as normal. However, when we then drove on dual and single carriageways, with speeds varying from 30 to 70 I noticed that the engine stuttered, jerked or hesitated slightly but noticeably if I accelerated by more than perhaps 1/3 throttle. My wife noticed the jerking from the passenger seat.

We did about 500 miles in that week and it ran smoothly in all other respects.

What are the possible causes of this engine issue?

I have been advised that it is possibly failed coil packs but a bit of googling suggests that failed coil packs would give far more serious or noticeable symptoms.

Could it need new spark plugs?

I will take it to the garage soon for their advice.

Thanks

MattMattMattUK

Did it only stutter when passing 1/3 throttle, or continually when trying to go beyond that? Eg. if you put your foot down would it stutter all the way up to 70mph, or only once for a second as you pass that throttle point in each gear?

Others might be able to offer better advice, my first guess would be a partially clogged fuel filter, but it could be lots of things, or a combination of things. 

Do you know anyone with an ODBII dongle you can plug in and get someone to have a look whilst driving, see if it flags anything that is enough to cause an issue but not enough to trigger an engine warning light?

Belenus

Thanks Matt.

The stuttering is intermittent and not continuous. It might stutter just once or twice, sometimes four or five times but never continuous. It only happens on harder acceleration not on gentle throttle.

A few months ago I had the by then over 9 year old original battery replaced as the stop/start no longer worked.

The garage plugged in their OBD (while parked not while being driven) which found no faults. The stop/start works as expected with the new Bosch S5 A11 battery.

I trust that garage as I have used them many times but I wanted advice about coil packs or other possible faults before I take it there.

Nobbie1967

Could be a faulty Mass Air Flow Sensor if they have one. Tells the engine how much fuel to inject, so if faulty you can get rough running.

WellKnownSid

If it's repeatable, then a scanner showing live data as you drive would be able to give you some proper direction - rather than firing off the parts cannon and hoping for the best.  You need fuel, air, compression, spark and timing to run an ICE - one of those is probably out of spec.