Intermitent overboost

[Andy C]

Another of the issues with the M100 I viewed today was intermitent overboost.

About 50% of the time under hard acceleration the boost guage went spastic and off the scale with no engine management cut off .. the rest of the time it sat just above .5. From my readings at LEC I assumed dodgy wastegate, or leaking hose/cracked pipe, or some such. Are my assumtions the most likely cause, or could there be something more sinister (read: expensive).

Thanks again for your musings

A&J

[Gazza]

Mine had the same problem, soon as you started the car it went to 0.4 and then off the scale when accelerating.

It turned out just to be a loose earth.

Gazza

[ESM]

I agree, a bad earth on the boost gauge transducer is the likely issue. Its mounted on the bodywork at the left side of the engine bay and has a pipe connected to it from the plenum as well as a couple of wires: one to the mount and one to a connector on the back of it. The connection of the wire on the mount will probably be the problem.

[Doug]

could also be a true reading if it has a BBR upgrade--you would know if it is true boost cause it should kick ass with the boost off the scale. but any erratic needle movement would suggest earthing problems with the sensor unit--so agree with above!