Is this 'shunting' or something else?

[rickprice]

I have a 450 with ACT carbon trumpets but otherwise standard intake system. Good leads and regular professional servicing means plugs should be OK.

When I drive between 2000-3000rpm, I get this constant irregular motion or hesitancy to the car, like a mis-fire or some such. The longer I hold the speed, the more obvious it is (or the more attuned I become to it).

It feels as if the car has a misfire; I get a gentle nudge in the back, where it kicks a bit. It almost feels as if I am driving along a slightly bumpy road and getting a bit of a rough ride - if hat makes any sense?

Lots of people describe shunting at 1200-1500rpm, where mine is very smooth.

Is mine 'shunting', or doing something else?

Rich

[MADMAX2]

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Phazed mentions shunting on this thread

[Robert Lees]

Mine does it too. I have 450 with act induction and trumpets. It reminds me of my old clio sport 2.0, when the extra valve timing opened. It doesn't shunt at low revs but more of a "pause" around 3000 rpm as though it is preparing u !. Someone suggested the vacuum advance / retard not working?.

be interested in comments. Again my leads, coil etc are all newish.

[Goaty Bill]

That's not what you would describe as 'classic' shunting. It's way beyond the normally associated rpms.

That said, what you are describing makes perfect sense, and sounds like shunting all the same.

This was a reasonably good discussion on 'classic' shunting causes and cures This shunting thing!.

[EGB]

Try it static in garage at 2-3000 revs. Then again in the dark to see if any cross fire shorts. Check no loose plug leads. My No 1 plug had a habit of half disconnecting. Ignition module perhaps.

[rickprice]

No sparks.

Have ordered plenum spacer...

See what happens...