Could this be the mass air sensor?

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DervMan - 15 Jul 2006 11:38 GMT

I'm still new to this GM / Saab TiD engine, but yesterday I was feeling
changes in engine behaviour (output) under acceleration. Some times I have
plenty of acceleration, sometimes I have next to no acceleration :) and it
was varying. This morning it was find...

It feels just like a petrol turbocharged donk when the ECU shuts down the
boost pressure because it was getting too high...

I'm thinking an intermittent problem with the mass air sensor, a DTi thing
on UK Vauxhalls and given the TiD's origins, sounds plausable. Is there
anything else it might be? A collapsed hose somewhere? Crud in the air
filter?

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The DervMan
www.dervman.com

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Tim.. - 15 Jul 2006 15:30 GMT

> I'm still new to this GM / Saab TiD engine, but yesterday I was feeling
> changes in engine behaviour (output) under acceleration. Some times I have
[quoted text clipped - 8 lines]
> anything else it might be? A collapsed hose somewhere? Crud in the air
> filter?

Unplug the AMM and go for a drive. If its now smooth, albeit down on power,
but consistent, then yes the issue is 95% with the AMM.

Tim..

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DervMan - 15 Jul 2006 18:53 GMT

>> I'm still new to this GM / Saab TiD engine, but yesterday I was feeling
>> changes in engine behaviour (output) under acceleration. Some times I
[quoted text clipped - 15 lines]
> power,
> but consistent, then yes the issue is 95% with the AMM.

AMM? *blushes*

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The DervMan
www.dervman.com

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John Greystrong - 15 Jul 2006 19:08 GMT

> AMM? *blushes*

Air mass meter, mass air sensor, etc.

John

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Moray Cuthill - 15 Jul 2006 23:03 GMT

I just had a thought about that technique. On the GM engine, it should cause
the engine to go into limp home mode, so it'll be very flat and only rev to
about 2500rpm (and on a Saab, it'll cause the engine management light to
stay on for 6 ignition cycles, IIRC)

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Moray Cuthill - 15 Jul 2006 16:42 GMT

> I'm still new to this GM / Saab TiD engine, but yesterday I was feeling
> changes in engine behaviour (output) under acceleration. Some times I
[quoted text clipped - 8 lines]
> anything else it might be? A collapsed hose somewhere? Crud in the air
> filter?

Also check for any split vacuum hoses, on the engine management piping side.
It's quite common for the rubber bits that link up all the plastic
pipes/solenoids/actuatos to split, and the plastic pipe to chaf through if
not secured properly. Any leaks in the vacuum system usually result in the
turbo wastegate not shutting properly (it's vacuum operated via a solenoid
valve), and a corresponding lack in power.

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