Strange hesitation at 4k rpm

[Jonff]

Got a bit of random issue that's developed.

Every now and then I get a weird hesitation in the throttle response at around 4k rpm in 4th and 5th gear, more so in 5th gear and only does it on light throttle, if I put a bit more throttle on the problem disappears. Best way to describe would be it's like the hesitation you get around 3k when the engine is cold, i.e when the car is running on the cold map. The problem is more apparent when I'm low on fuel so I'm thinking possibly a fueling issue? Can't see it being an injector as surely the problem would be there constantly? so I'm thinking along the lines of possibly a clogged up fuel filter as I'm sure the car is on the original filter when it came out the factory.

I'm a bit stumped by it really, I've cleaned the throttle body and replaced the the throttle cable, although it did seem to ease the problem a little it's not cured it. Anyone have any other suggestions?

Car's a ph-1 172 btw.

 

[f0xy]

Id change the fuel filter for the sake of a couple of quid for the sake of it and see what happens

 

[Jonff]

Yeah I was going to just for the sake of knowing it's done then. Pretty sure it's beyond it's best now it's done 98k lol.

 

[Christopher]

Oxy sensors and coil pack should be looked at. Is it fine when it's cold? Just at those specific revs?

 

[Jonff]

Yeah behaves as it should when cold and yeah only ever does it at 4k rpm in 4th and 5th gear.

 

[Jonff]

Swapped fuel filter this morning after getting a face full of V-power lol. Took the car out before and there was no hesitation, may have cured the problem but only time will tell.