Rattle Under light throttle use ZT 190

[StarmistBlue400]

My ZT 190 (65K on clock) has developed an odd rattle.

You cant hear it on idle or hard acceleration. It can only be heard when coming off the throttle to change gear or if you lightly feather the throttle, you can keep the noise going by doing this.

Its a light knocking/tappety sound and fairly loud. Any ideas?

[Mr2Mike]

Probably the infamous VIS linkages have worn within the manifold. These control a set of butterfly valves that change the effective length of the inlet runners (and there is another separate system to change the plenum volume), and when worn the butterfly valves get rattled by the induction pulses within the manifold. A significant thorn in an otherwise great engine, since they aren't easily repairable and new manifolds are pricey.

[Ex X Power]

Agree with above

[StarmistBlue400]

Took it to Beech Hill (local MG specialist) and it needs a top end rebuild. I've starved it of oil at some point. Only cost me £1100 so I'm going to run it till it dies shame really because its only done 65k

[Mr2Mike]

Oh bugger, that's not good. I'd have thought a pair of low mileage s/h heads would have been cheaper though.

[Pipster1969]

Mr2Mike said:

Probably the infamous VIS linkages have worn within the manifold. These control a set of butterfly valves that change the effective length of the inlet runners (and there is another separate system to change the plenum volume), and when worn the butterfly valves get rattled by the induction pulses within the manifold. A significant thorn in an otherwise great engine, since they aren't easily repairable and new manifolds are pricey.

VIS motors are easily repaired and upgraded through the MG & ZT owners club, pretty cheaply as well.

[Mr2Mike]

Pipster1969 said:

VIS motors are easily repaired and upgraded through the MG & ZT owners club, pretty cheaply as well.

The VIS motors are usually very simple to repair as a DIY job, but they don't necessarily cause the manifold rattle. The main cause of this is wear in the balljoints formed in a nylon rod that connects all the butterflies together. The wear can get bad enough that the balljoints fall apart so the butterflies are free to flap about. You have to cut the manifold open to gain access to this part and no spares are available so it's a very labour intensive DIY repair.

[Lates600]

Definitely worth looking into the power vis motor and linkage, quick easy fix and confirm either way.