specific running isue

[newt]

ok i have noticed a slight problem with the running of my g40,
its a slight splutter that clears with a little more throttle or revs
the "time" it happens is
2k rpm
coolant guage at 70 degrees
foot resting on the throttle
any gear
steady road speed

im thinking its in the map, reason being the car except from above is flawless in performance etc
my "guess" is that its a little rich at this point and cant burn the fuel easily, its just before the lambda comes in to effect (temperature wise) but the engine is walm , it only does it once per journey which is also why i think its temp related
at the point it does it my foot will be only resting on the throttle so just of the stop and i would be cruising along at sat 30 or 40 mph , a little more throtte and it goes away , a little bit more revs and it goeas away (or becomes less apparent) or the tempgoes up another 5 degrees ,

before anyone mentions
it has a brand new genuine coolant sensor (blue)
new cap, arm, leads etc recent service
no vac leaks, been over every thing with carb cleaner whilst running
throttle butterfly is clean


any one experienced thisbefore?

[Jezza-7]

Have you done the boost return mod?

[newt]

yes , vents to atmosphere

[Jezza-7]

Is the breather pipe ok? Ie no kinks?

[newt]

what difference would the beather make?, it is however ok

im thinking lambda is up the shoot as its getting worse

[newt]

is running rich at idle and fuel economy is down 

[MartinB]

May be worth replacing the lambda or swapping for a known working one to eliminate that.

[Jezza-7]

If i still have my working one, i could send it to you to try out?

[newt]

was thinking about it and also my mate come round in his g40, we measured blue coolant sensors on each car and all read the same,
the running issue is also there when the car is cold which eliminates lambda , as the lambda is not used till the engine gets walm.
until i checked my mates g40 and measured the resistance i was starting to think it was a dodgy blue sensor but im now not so sure,
what else could cause rich running

[newt]

think i may of found the problem, the lambda is not switching, i have a new one on order for tomorrow so will get it fitted and hopefully should all be well
im thinking the oil from my slightly weepy charger finished it off,
im waiting for a rebuild kit for my spare r1 charger

[newt]

new lambda fitted seems like problem is solved, car is now economical again and isn hesitating any more