Full bore miss fire

[TuxMan]

went out last night for a blast ....just had to be done !! and i got a couple of hiccips on full boost ,did it on the rolling road day but has not played up since wonder if it could be plug gap as i gapped them at 40thou but have since read 36thou is better , does not feel like fuel as its a very sudden hiccup also if i,m gentle with the boost and feed it in rather than just flooring it,it does not do it any ideas guys ??

Edited by TuxMan on Friday 26th June 09:02

[mikey_p]

Fuel pipe between tank and fuel pump collapsing?

That was the cause of the exact same symptoms you are getting in RobPs car. Although it was only even when heat soak had set in. There are numerous posts about it on here if you have a search.

[art411y]

never had a problem with having mine gapped at the 40 thou suggested .i also need to change that pipe but as yet ive not suffered the collapse.maybe its because i dont really use the car as it should be used

[Duke Thrust]

Hi Simon,

It sounds like you have the same problem as me. The waste-gate actuator shaft on the front turbo has warped ever so slightly and it sticks causing the cough as the boost map goes bonkers for a second.

I need to take the turbo off and get the shaft/housing machined.

[TuxMan]

have inspected pipe earlyer in the year and it looked in good order ....over the winter i,m going to change all the fuel system ,tank was full to the brim so would have thought there would be enough gravity pressure to keep pipe expanded ?? will have another look over the weekened . simon

[S26VE P]

Fuel level will not make a difference, the pipe is on the verge of kinking so once warm it does. Mine doesnt seem that bad to look at but on the odd hot day out i do think it causes a possible issue as only when very hot there is a slight hesitation.

[Adrian W]

Duke Thrust said:

Hi Simon,

It sounds like you have the same problem as me. The waste-gate actuator shaft on the front turbo has warped ever so slightly and it sticks causing the cough as the boost map goes bonkers for a second.

I need to take the turbo off and get the shaft/housing machined.

have applied vacuum/pressure to prove this?

[Duke Thrust]

Adrian W said:

Duke Thrust said:

Hi Simon,

It sounds like you have the same problem as me. The waste-gate actuator shaft on the front turbo has warped ever so slightly and it sticks causing the cough as the boost map goes bonkers for a second.

I need to take the turbo off and get the shaft/housing machined.

have applied vacuum/pressure to prove this?

Yep, hand held pump, you can see it sticking as the pressure rises and falls.

[Gadgeroonie]

sounds like a temporary boost spike

what does the boost read when it does this ?

[Mike Tuckwood]

We have seen this on the dyno recently, sticking wastegate shaft, not fully closing, and sticking the hotter the car gets causing differing boost profiles for no immediately apparent reason, then getting worse and causing overboost/boost spikes.

Re machine of wastegate penny shaft required to fix.



Mike

[TuxMan]

thanks for the replies guys , lots to look at !!! according to mikes boost map on rolling road there is no spike in the boost or lean run spot on the graph .. so still not convinced its a boost or fuel related problem although i will check the car out over the weekened .

[Duke Thrust]

Did you get to the bottom of this Simon?

[TuxMan]

Yep re-gapped plugs to 36thou , seems to be fine now .