violent jerking at 2000rpm?

[teamcmc cl]

im pulling my hair out, my g40 seems to have some problem at the mo, when i reach 2000 rpm it kangaroos once and then carrys on going, i think its poss fuel related, it seems like the kind of jerking that happens when your just about to run out of fuel, (but its not) its like its some sort of fuel starvation, fuel filter is 6months old, checked fuel pressure from pump and in rail at idle both seem to be fine cant see any sort of air leaks ect, injectors have not long been reconned and injector timing at idle seems to be ok. might try another fuel filter tomorrow just incase its that, just seems wierd that it does it at 2000rpm in every gear. has anyone come across anything like this, would really help. 

[PeteG40]

how old are your ignition components? have you checked timing?

[teamcmc cl]

plugs are about 2000miles old leads are 12months old, i tried a spare coil pack i had, no difference, and i put a new cap and rotor arm on tonite, did the timing 12 months ago, as far as im aware its not moved. i thought it could be ignition related too but i think ive tried mostly everything on that side, no fault codes in the ecu either. puzzled.

[PeteG40]

d you have an air fuel ratio meter

[teamcmc cl]

no i dont unfortuntely, ive tried a new fuel filter on it today and blew both the fuel lines through but still no good. back to square one. 

[PeteG40]

what chip is fitted?

[teamcmc cl]

its got a psd one that i got off someone via clubpolo, its "apparently" mapped to suit a setup consisting off full blend, toothies, 4branch, exhaust, gt inlet and greens ect, its only been in two weeks. i fitted it the same time as the greens, gt inlet and 4 branch. i thought it could be due to this but its ran sweet as a nut for the last two weeks. 

[tdh-syorks]

i changed mine a few months ago and it ran sweet for the first 2 weeks then i started getting similar problems, tho mine was more to do with firing the car up, i had to really turn it over and give it some throttle, i also noticed it was running too rich. i spoke to a bloke i know who used to own a few G40's and he said its because the chip had to be properly mapped to your exact specification all the way down to the coolant temp sensors. so all i did was put my old chip back in and the problem was cured straight away,
Not sayin it will in your case but it's worth checking it out.

cheers Tom

[hayesey]

I'd try swapping back to the old chip and injectors (assuming your old chip isn't for 250cc "green" injectors).  Certainly using the wrong chip can cause issues...  It's not really right to say that you HAVE to have a custom map made to suit your car.  Yeah if you want the maximum power out of the setup then yeah a good custom map will do that but a more generic map should work just fine.  A custom map will also only be as good as the person who maps it for you.  The same can be said for generic chips but you'd have thought they would have been tested etc...

[lance]

have you had it on the computer mate?

see what comes up if you can get it on a snap-on scanner or summat.

could well be your chip tho also could be the in tank pump not feeding the inline pump with enough fuel under load but i wouldnt be keen on driving it round like that just in case.

[teamcmc cl]

thanks for all your imput guys i put my original g40 injectors and chip back in and still not cured, i even put some more fuel in thinking it could have been some dodgy fuel but to no avail, its been on my snap on scanner, no fault codes and all the sensors seem to be doing what they should be, its wierd. i think i might be looking to either the crank sensor or distributor next, purely because its doing it at that specific rmp range. im really pulling my hair out now lol.

[tdh-syorks]

ok, know it might sound silly but i'd change the fuel pump relay, for the small amount it costs for one, about 7 quid it eliminates the fueling problem i'd say.

cheers Tom

[PeteG40]

there is no crank sensor!

have you checked fuel pressure?

[teamcmc cl]

ah that must be a knock sensor on the back of the block then, well the dist usually play up so il try my mates off his g40, i did think about changing that, does anyone know where the fuel pump relays are on these?

[PeteG40]

knock sensor doens't do that much really on a g40.

the fuel pump relays are up by the ecu - one is a fuel pump relay and the other a relay for the ECU