XP Loss of boost.

On 1 Aug 2008 21:26:20 GMT, Adrian <toomany2cvs.TakeThisOut@gmail.com> wrote:

>Colin Stamp <col.dustbin.TakeThisOut@stamp.plus.com> gurgled happily, sounding much
>like they were saying:
>
>> My 2001 Saab 9-3 Aero seems to be slowing down a bit recently...
>>
>> It has a "turbo" gauge, which seems to be a boost gauge without a scale,
>
>I can't remember for certain if it'd apply to an NG9-3, but the boost
>gauge on most recent Saabs isn't actually a "boost gauge", but a sort of
>ECU-controlled "load gauge", the calibration of which can be amended via
>the diagnostics...

Yep, now you mention it, I think I remember the service manual saying
it shows injector pulse-width, so it's more of a torque gauge than a
boost gauge. It hasn't been re-calibrated though, so the differences
in the readings are down to some real effect.

>
>First port of call, though, would be to see if it still does it on
>another tank of fuel, in case it's knocking back boost after seeing
>pinking. I'd also go over all the pipework - make sure there's no bleed-
>off from a duff vac hose somewhere.

I wondered about knock too, but it's been doing it through several
tanks from several petrol stations. I've only had a quick look at the
pipework so far, but I might get a better chance later today...

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

Colin Stamp wrote:

> The air filter is getting on a bit, so I guess it could be that. Does
> anyone have any other ideas? control system?

A blocked air filter can do all manner of nasty things to any engine. I'd
try changing that before anything else.

Si
 >> Stay informed about: XP Loss of boost. 

On Fri, 01 Aug 2008 22:05:36 +0100, Colin Stamp
<col.dustbin DeleteThis @stamp.plus.com> wrote:

Well, I had some time to do a bit of poking around today, so I tried
taking out the air filter - no change, so that was that off the list
of suspects.

The vacuum pipes for the dump valve looked a bit dodgy, so I thought
maybe they ware causing the valve to leak air round the bypass loop. I
tried it with the control pipe to the valve disconnected and plugged,
which gave me low boost right through the rev range, which was
inconclusive. So instead, I plugged up the bypass pipe. That gave me
the original symptoms back, so I guess the dump valve and it's control
system is off the hook too.

It could still be the dodgy vacuum tubes though. They share an inlet
manifold tap with the fuel pressure regulator so I guess, if they were
leaking, they might cause knock through low fuel pressure.

I've also finally RTFMd a bit, and I found a section entitled "Air
mass limitation" which has a graph showing the torque reaching its
maximum value at 1.8K RPM and then starting to ramp down at 5K. That
doesn't really tie up with what I'm seeing now *or* how I remember it!

I think I'll just change the vacuum hoses and then forget about it,
whether it fixes it or not. I'll be trading it in soon anyway...

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

On Sat, 2 Aug 2008 18:41:43 +0100, "Mungo "Two Sheds" Toadfoot"
<eastREMOVEkent.DeleteThis@gmail.com> wrote:

>Colin Stamp wrote:
>
>> The air filter is getting on a bit, so I guess it could be that. Does
>> anyone have any other ideas? control system?
>
>A blocked air filter can do all manner of nasty things to any engine. I'd
>try changing that before anything else.
>

I must admit, I had my hopes pinned on it as a nice easy fix, but I've
since tried it without the filter in and it's still the same (

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

On Fri, 01 Aug 2008 22:05:36 +0100, Colin Stamp
<col.dustbin RemoveThis @stamp.plus.com> wrote:

>Hi all,
>
>My 2001 Saab 9-3 Aero seems to be slowing down a bit recently...
>
>It has a "turbo" gauge, which seems to be a boost gauge without a
>scale, but white, orange and red segments instead. The boost limit is
>slightly into the red. I'm fairly sure I remember it, in the past,
>being able to get into the red below 2K RPM, then staying there
>solidly until the red line at 6K.
>
>Now though, I seem to need at least 2.5K to get into the red and it
>falls back into the orange slightly at something over 5K. Needless to
>say, the edge has gone off the acceleration.
>
>The air filter is getting on a bit, so I guess it could be that. Does
>anyone have any other ideas? control system?
>
>Also, can anyone with the same car confirm that the way I remember it
>is correct?
>
>Cheers,
>
>Colin.

It's not got a little bit more rorty has it? A leak on the
manifold/turbo sounds quite good until it's gross and then it sounds
like a tractor. An exhaust leak before the turbo will reduce flow
though turbine giving late spool and low boost. Grope all the nuts on
the turbo flanges to check security.

A leak after the turbo reduces backpressure and thus pressure drop
though turbo giving more boost. A 3" drainpipe exhaust does the same.
--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!
 >> Stay informed about: XP Loss of boost. 

IF the air filter is "getting on" maybe its time for a thorough service
(and as its a turbo - "decent" high quality Oil)
 >> Stay informed about: XP Loss of boost. 

On Sun, 03 Aug 2008 09:59:09 +0100, Peter Hill
<peter.usenet1.DeleteThis@nospam.demon.co.uk> wrote:


>
>It's not got a little bit more rorty has it? A leak on the
>manifold/turbo sounds quite good until it's gross and then it sounds
>like a tractor. An exhaust leak before the turbo will reduce flow
>though turbine giving late spool and low boost. Grope all the nuts on
>the turbo flanges to check security.
>
>
>A leak after the turbo reduces backpressure and thus pressure drop
>though turbo giving more boost. A 3" drainpipe exhaust does the same.

The exhaust seems solid and there aren't any audible leaks. I'll have
a closer look when I change the control hoses for the dump valve.

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

On Sun, 3 Aug 2008 10:12:19 +0100, "Tommy" <tttoommy.RemoveThis@googlemail.com>
wrote:

>IF the air filter is "getting on" maybe its time for a thorough service
>(and as its a turbo - "decent" high quality Oil)
>

The filter is about 30K miles old, which makes it just due for
replacement, though I've always thought 30K miles is quite old for an
air filter. It's out of the picture now though. I do the oil/filter
around every 6K miles against the 12K recommendation. The other
service items are generally up-to-date. Are there any other routine
service items that might affect this?

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

"Colin Stamp" <col.dustbin.RemoveThis@stamp.plus.com> wrote in message
news:mh8b94hrff0hpaccflianbv1dka4a5d92f@4ax.com...
> On Sun, 03 Aug 2008 09:59:09 +0100, Peter Hill
> <peter.usenet1.RemoveThis@nospam.demon.co.uk> wrote:
>
>
>>
>>It's not got a little bit more rorty has it? A leak on the
>>manifold/turbo sounds quite good until it's gross and then it sounds
>>like a tractor. An exhaust leak before the turbo will reduce flow
>>though turbine giving late spool and low boost. Grope all the nuts on
>>the turbo flanges to check security.
>>
>>
>>A leak after the turbo reduces backpressure and thus pressure drop
>>though turbo giving more boost. A 3" drainpipe exhaust does the same.
>
> The exhaust seems solid and there aren't any audible leaks. I'll have
> a closer look when I change the control hoses for the dump valve.
>

Does it have a MAF sensor that could be gummed up? I know they're famous on
VAGs for manking easy and just giving random symptoms including things like
these... I'm not a specialist though, I'm betting others can give better
advice.

--
Dan
Clio R27 F1 #65
 >> Stay informed about: XP Loss of boost. 

On Sun, 3 Aug 2008 22:34:14 +0100, "DanB" <iridiumdan DeleteThis @googlemail.com>
wrote:

>Does it have a MAF sensor that could be gummed up? I know they're famous on
>VAGs for manking easy and just giving random symptoms including things like
>these... I'm not a specialist though, I'm betting others can give better
>advice.

Hmmm. Sounds plausible - I guess anything that could cock up the
mixture might be the cause. I'll check that too.

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

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 >> Stay informed about: XP Loss of boost. 

On Sun, 10 Aug 2008 19:31:43 -0400, - Bob - <uctraing RemoveThis @ultranet.com>
wrote:

>Hav eyou changed the plugs in the last 10K miles? If not, do it and
>use stock NGK's. Replace all those vacuum lines - you can do it with
>10' of hose in 20 minutes.
>

I finally got round to doing the vacuum hoses yesterday. No change...

It's an interesting point about the spark plugs. They're a little over
20K miles old. The change interval is supposedly 30K. I think they
might have to go anyway.

I think the car knows I'm thinking of getting rid of it. It even
started demanding a service over the weekend!

Cheers,

Colin.
 >> Stay informed about: XP Loss of boost. 

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