Pulsing at high rpm/ load/ speed

[dan_b]

Yesterday I took my A2 on a private test track (ahem) for a bit of an Italian Tune Up (honest guv.). In 4th and 5th gear, above about 3300rpm on full throttle, the car started to develop a strange pulsing sensation whilst accelerating - the surge/hesitate cycle would be with a frequency of about 1 per second. In 5th it felt like the car would have struggled to keep going towards its theoretical vmax - even though I have a remap and a longer 5th...

The car didn't trigger limp home and there was no excessive smoke or anything else, just this odd pulsing. The air temperature was pretty chilly yesterday - about 2C so the charge would have been very dense.

I'm thinking that it was the N75 trying to modulate full boost but not very successfully? Perhaps the N75 is faulty? Or is it the wastegate? Or is it a dodgy/ stuck EGR valve - I would imagine on that kind of full load there would be a lot of exhaust gas to recirculate?! Or is it something else?

I've not driven the car in anger for quite some time as I'm on my econo-drive these days, but felt the need yesterday. Hope there's not something expensive going on?! It wasn't doing it in the summer when the car got some similar treatment after I'd solved the overboost problem...

 

[humps]

may be the injector?

 

[a2sumo]

Blocked fuel filter? Sounds like fuel starvation. Good luck

 

[dan_b]

Hmm, good thinking, how often should the fuel filter be changed?

 

[A2Z]

I thought the same to be honest.

Should be changed at least every other year in my book but better annually.

I find it quite incredible the amount of 'stuff' that comes out the fuel filter (and the pollen filter for that matter) when you replace them, which lots of people neglect to do very often!