Fuel related knock?

[Dr_Rick]

So, filled up at Morrisons at the weekend, and only had 'Standard' unleaded available. Put in around 3/4 tank.

Took the car out today and drove 35 miles each way for work. Noticed that when pulling away from a stop, WOT under load I got a 'stutter'.

At motorway speeds it wouldn't reproduce. Google Gemini suggests knock due to poor fuel octane / quality, and a solution of putting a dose of octane booster in and top up 1/4 with Super unleaded.

Never had this before, so, sound reasonable?

[Simon_GH]

My WOT stutter (Focus 1.5 petrol turbo) turned out to be a faulty coil pack. It didn’t cause any fault codes to be logged so I discovered it purely by a process of elimination (spark plugs are a more likely cause). I’d be surprised if a car didn’t adjust its timing etc. to suit the octane rating these days.

No harm in trying the premium fuel though. That was my first port of call.

[Panamax]

I'm sure modern cars are supposed to adjust to whatever fuel is put in them. Knock sensors and all that stuff, plus electronic advance/ retard.

[Dr_Rick]

My plan is to try, in this order:
- Octane booster / top up with 97 / new full tank of Super UL
- Plugs
- Coil packs

Note to self - don't scrimp on fuel quality, just drive a little further to get 'the good stuff'.

[Simon_GH]

Dr_Rick said:

My plan is to try, in this order:
- Octane booster / top up with 97 / new full tank of Super UL
- Plugs
- Coil packs

Note to self - don't scrimp on fuel quality, just drive a little further to get 'the good stuff'.

This was my approach. Also, I only bought one coil pack and planned to swap it between cylinders (£50 from Ford). Luckily (after months of head scratching with the initial stuttering issue) I tried the last cylinder first (Sod’s Law) and it fixed the issue.

[Boylston]

Try changing the mass air flow sensor. My Evora 400 got lumpy, etc and then ultimately started throwing strange engine fault codes.

After changing it runs so much smoother and zero engine fault codes.

Simon

[Dr_Rick]

So far, suggestions include:
- Octane booster
- Increased RON fuel
- Replace sparkplugs
- Replace at least one coil pack
- Replace MAF sensor

Any more for any more?

[Dr_Rick]

Right, 1/4 tank of Tesco Momentum 99 added, plus the bottle of Lucas Octane Booster.

A few miles of non-aggressive throttle driving and I'm 99% I can feel the difference. Idle is stable and the revs feel 'finer' if that makes sense.

After a good few mins and miles I tried a few tests, like 2nd gear / 20mph and loaded gently to 50% throttle - no stuttering. Then 3rd / incline and loaded to 50% throttle - again, no stuttering.

The car is back to feeling more urgent too. So I think I'll stay away from Morrisons fuel from now on.

[CSR Performance]

Might a simplistic thought, but have you plugged in a code reader just to see if it gives you any pointers towards a specific cylinder?