[Lfk]

I always fill up at either Shell or BP. About a month ago I was out of gas and used a Caltex that was on my way. I started feeling a slight acceleration lag after this. Two full tanks later (back to BP and Shell), the lag isn't going away.

One time when I was pulling off it was so bad I actually thought something was physically blocking the car (as if it's going over something). And the worst part is it happens even in Sport+. It's not as pronounced, but even at a high rpm there's a discernible lag when I step on the gas.

What could be wrong? Do I need to take it in and have a mechanic look at it?

[erawamai]

Originally Posted by Lfk

I always fill up at either Shell or BP. About a month ago I was out of gas and used a Caltex that was on my way. I started feeling a slight acceleration lag after this. Two full tanks later (back to BP and Shell), the lag isn't going away.

One time when I was pulling off it was so bad I actually thought something was physically blocking the car (as if it's going over something). And the worst part is it happens even in Sport+. It's not as pronounced, but even at a high rpm there's a discernible lag when I step on the gas.

What could be wrong? Do I need to take it in and have a mechanic look at it?

I can't say I've experienced this. Warmer weather affecting the turbo?

[oz555]

Contamination in fuel is the cause. You should empty and clean the tank. Check the injection system too.

[Lfk]

Originally Posted by oz555

Contamination in fuel is the cause. You should empty and clean the tank. Check the injection system too.

What's the procedure for that? Is that something I can do myself?

[thewusman]

Originally Posted by oz555

Contamination in fuel is the cause. You should empty and clean the tank. Check the injection system too.

Was going to echo this. And maybe contaminant in the high pressure fuel pump.

Had this issue in a previous Audi S4.

[oz555]

Originally Posted by Lfk

What's the procedure for that? Is that something I can do myself?

No. You must go to BMW service for that.
After that try to find something similar to this https://www.amazon.co.uk/Universal-M.../dp/B07R7VZSP7
Of course, the flow must be compatible with engine requirements but this little cheap thing prevent problems with petrol contamination.

[Lfk]

Originally Posted by thewusman

Was going to echo this. And maybe contaminant in the high pressure fuel pump.

Had this issue in a previous Audi S4.

Originally Posted by oz555

No. You must go to BMW service for that.
After that try to find something similar to this https://www.amazon.co.uk/Universal-M.../dp/B07R7VZSP7
Of course, the flow must be compatible with engine requirements but this little cheap thing prevent problems with petrol contamination.

Thanks guys. Made an appointment for Thursday. Should I avoid driving the car until then?

[Lfk]

One more thing. The lag is definitely not like it was with that first tank. I wonder if I've also become more attentive to this after the initial issues.

For example, on Sport+, there's a lag if I smash the throttle and the engine is revving under 3000rpm. While that annoys me a lot, I also wonder if I actually floored it like this before. Regardless, is any lag acceptable in Sport+? I found contradictory answers when I Googled it.