Missfire or something else

[jas98]

Hi all...what I thought was tailshafe shaking I'm not sure now. Ba xr6t stock tune

 

Basically when giving it some...like medium to heavey acceleration from stand still for example ..there a pretty noticeable shack in car that I can feel in accelerator lightly but really shakes car...feels like engine is lagging heaps ..also seems to only boost at like 2 psi...kinda like it hits a dead spot.....

 

 

Accelerating slowly like a granny it seems ok...yes it using up a bit more fuel...it's never been great on fuel though 

 

Now it seems to do this not allllnthe time but say 90% of the time 

 

Forscan gives zero codes. Could are genuine...prob have like 50 000ks on em. Spark plus about 15 000ks. All intake gaskets are fine as was replaced not long ago. 

 

Basically I have had dead coils in past and it's always Benn the brrrrrr brrrr type missfire...this ones a shake . 

 

I have checked fuel filter and it was fine but I changed it anyway...I'm thinking it's a missfire as like I said it's chewing more fuel but I would have thought I'd get a code for a missfire?

[xr6tForMe]

I dont think the BA gives a code for misfire?

[xr6tForMe]

Have you gotten any further with this?

Re: intake manifold gasket.

I replaced one recently a little while back on my BA wagon.

Idle was rough, but under acceleration the engine felt close to normal.  I think that is because with throttle closed, there is more vacuum and a greater proportion of air (ie way too much) gets sucked into the intake/cylinder.

With throttle open, there is less vacuum to suck unmeasured air in and a greater proportion of correctly measured air going into the cylinder through the intake manifold, so the air fuel ratio is much closer to correct.

Its been a long time since I had issues with coils on the BA, but I did replace them once with cheap coils and they failed quickly after replacement.

I dont think I had any codes with forscan, but its a long time ago that it happened.

It was a real pain because I incorrectly ruled out the coils because they had been replaced.

Maybe check the plugs?  See if the gaps look ok, that there are no marked from arcing down the insulator and that they all look the same colour?

Using more fuel seems to indicate engine problem, rather than driveline, but I think tailshaft shaking happens worse under heavier load than under light load.