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Discussion Starter · #1 ·
Hi all
I'm a complete newbie to saabs, let alone aeros, and I have a few performance and technical querries.
Firstly, I believe there is a mechanical problem with my car that is limiting its power. This may or may not be the the result of several faults as it is manifested in several ways. For one thing, if I am driving the car hard, and especially in the middle gears, there can be a sudden thump as the engine seems to loose power for a second and then regain it. I am told this is probably the engine management shutting down the fuel supply to protect the turbo from over boosting.
This seems to fit with another observation...that the boost gauge goes slightly into the red and pulses there. I can feel the pulses dumping the power such that the car goes faster if I lift off the accelerator a little so that the boost drops into the red hatched area. When I bought the car there was a brass valve fitted in hte vacuum pipe to the turbo that allows the boost to be fine tuned ( so I'm told) and using this I can drop the max boost to just below the red, avoiding the alarming sudden engine cuttouts, but also limiting the power of the engine. It has to be said that, even with the turbo boosting just into the red it does not give the perfomence I was expecting. Have I become so used to the increased performance already (my last car was a 1.8 cavalier) so that I am no longer impressed by it? I would have believed it if it wasn't for the cars that seem to be able to out pace me, e.g. golf GTi's, v6 mondeos, etc.

Am I expecting too much of this car?
Is there a likely cause of a lack of power?
According to HPI it is registered as an aero from new. Is it possible that incorrect part replacement or something of the sort has reduced the power?

Any help greatly appreciated.
Kev
 

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Kev,
The overboosting/fuel cuttoff and pulsing problems are probably the result of a faulty Boost Pressure Control Valve (black plastic thingy mounted to the top nearside end of the rad bracket) I had identical symptoms to you and this is what it was. It could though, be a sticking wastegate, but I'd have the BPCV checked out first, by replacing with a known working one if you can.

The brass fitment sounds like a MBC (manual boost control) valve, but if the BPCV is faulty then this will have not benefit other than be able to back off the boost to prevent the fuel cutoff coming into play, which would account for the lack of


Other's with more technical knowledge may be along later to offer more help.....
And welcome by the way......looks like another member joining the Scottish 9K Aero mafia.....
 

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Hi Kevster and welcome to Saabscene.

Firstly, don't worry about the rapidity of your car... in stock form the Aero is more than a match for most things on the road these days.

However it does sound like it's not running right.

The brass valve is almost certainly what's known as a bleed valve. Without going too much into the theory, it does as you suggest enable extra performance by increasing the turbo boost pressure. It sounds like you are hitting the overboost protection limit.

The Trionic APC system fitted to 9000s is adaptive, and one of the things it adapts to is overboost- basically every time it happens, it slightly lowers the threshold at which it will occur next time.

Before going any further with diagnosis, I would recommend that you disconnect the battery for 20 minutes or so (remember to check your radio keycode first of you have one) and fully close the brass valve.

When you reconnect the battery, take the car out and perform an adpatation run as described here on BillJ's 9000 site.

If you're still having problems with overboost then, it may be a faulty APC solenoid.

The Trionic system is also very sensitive to spark plugs- it's worth checking that the correct ones have been fitted (NGK BCPR7ES11) and have been changed within the last 12 months. Do not use anything other than the specified NGK plugs.

HTH
 

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Discussion Starter · #4 ·
Cheers Guys
Aeropilot...thanks for the welcome. I am glad to be part of the aero club, but will be happier once I feel I'm driving the real deal. I like the terminology 'black plastic thingy mounted to the top nearside end of the rad bracket'. It is exactly the technical level that I think at. I'll see if I can get hold of a BPCV to try your suggestion out.

Mark...I'll give that a go tonight. Can't say as I enjoy the 'shut downs' if thats what they are, but I guess I'll have to go through a few before the APC finds its feet again.

One more detail I forgot to include in the orginal post, performance and the 'shut downs' are worse some days than others. Is this likely to related to air pressure?

Thanks again
Kev
 

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Welcome to the board Kevster

Once you have the Aero sorted, Golf GTi's, V6 Mondeo's and Vectras will all be easy prey


Certainly my old 2.3 Carlsson (220BHP) would wipe the floor with any of our many company Golf 1.8T GTi's
 

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Originally posted by Kev Mc:
[qb] Once you have the Aero sorted, Golf GTi's, V6 Mondeo's and  Vectras will all be easy prey            :fawlty:      :fawlty:  
[/qb][/b]
Hey even a NSX isn't that quick in a straight line, hehe , as a certain owner found out a little while ago.

Welcome to the club Kevster .

Nick.
 

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If you do need a BPV and are going to buy new, you may have trouble as it is not a stock item for saab dealers. However, I do know that Brecks Saab in york 01904 520300 has one in stock and it is £130, eeeks.

The good second hand route does look appealing!

Good luck
 

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Discussion Starter · #10 ·
Simon
Thanks for that. I have a similar price from my local saab dealer (local being 60 miles away....thats scotland for ya). I take it this is strictly a saab item and no independant makers? I think I'll see if I can borrow one for a tryout before ordering. BTW, what's the best way to track down second hand aero parts? I'd have thought there would be a risk of picking up a part with the same problem. Also, cant' imagine many aeros being brocken for parts. Is this specifically an aero part or is it common to other models?

Are BPCV's servicable? Might have a look at mine tonight.

Sorry for the list of questions. I'm just keen to get out there and burn some NSX ( Nick).

Kev
 

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Discussion Starter · #12 ·
Reading the woes of some others on this forum has gotten me thinking of another thing that I was unsure of. Between each gear change I can hear the dump valve depressurizing the system. Its much louder than I had expected for a car that was orginally intended to be more exective than racer. The dump valve appears to be the original one. How loud should it be?
Kev
 

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Discussion Starter · #13 ·
Hi Mark
I havent tried it yet. I know most of the country was dry yesterday but it rained here all day. After reading the article you suggested I thought speeds of up to 105mph an wet local roads might result in some more dramatic mechanic problems involving stationary objects
. I had a bit of a test run on a hill near my house but after spinning the wheels in fourth I decided to give it a miss. It hasn't rained here for a month and all the oil seems to have built up on the road. Great skid pan but I didn't fancy my chances on the corners.
Maybe tonight
Kev
 

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Kevster,

Which Saab dealer do you regard as your local? There's a Saab specialist (St Clair Saab) in Kirkcaldy that I'd recommend and there's also Westcars in Perth.

If the previous owner modded the car slightly the noise might be an atmospheric dump valve. I've had the Abbott (Forge) recirculating dump valve fitted and it's quite noticeable as well. I can't remember if I noticed the standard Aero valve before it was swapped.
 

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Discussion Starter · #15 ·
Hi Gordy
I didn't think st clair dealt in spares. I may be thinking of the wrong place though. I didn't know about the Perth saab dealer. I'll look them up and give them a ring.

re the dump valve noise...what would the result of an atmospheric dump valve be, other than increased noise? I presume that if abbot do a re circulating one then this is preferable. Is the original saab dump valve re circulating?

Another question I've thought of...my aero is not a 1994 (misstake in the heading there..oops) but a 1993. I believe this makes it one of the earliest aeros. Were there any glitches on the earliest cars (as is so often the case with a new model) that was sorted out on subsequent models?

Kev
 

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You should use a recirculating dump valve. The fuel injection system monitors the air in the system to set the mix, by dumping to atmosphere you are changing the level after it has been measured, ie., the ECU doesn't know the amount has been changed. Simply put you end up with all sorts of driveability issues.

IIRC Billj has written he can hear his standard SAAB dump valve. I can certainly hear my Forge one.

As to your bleed device: it'd be interesting to know if the previous owner had installed it to overcome a faulty BPCV rather than to improve performance. OTOH if boost has been increased it might have blown off one of those annoying small bore vacuum hoses (which would affect
). I'd check them for security on the nipples and for any pin hole cracks.
 

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Discussion Starter · #17 ·
Cheers Steve
Hey, this site is great. I could have spent endless days fiddling about totally in the dark about the likely causes of the problem and wasting cash along the way.
Now at least I have a sensible place to start and a reasonable idea of how to go about it.
Kev
 

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kevster,

You're probably right about St Clair not having much in the way of spares. If I'm up in Dundee soon I'll PM you for a meet so you can listen to mine for a comparison. In fact what are you doing this afternoon, I'm bored at work and I can pop up to Dundee for a skive. I could be there for 3 o'clock.
 

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Discussion Starter · #19 ·
Well it was a pleasure to me you Gordy. Between us we managed to throw some non technical guess work on the situation and you've identified a few of the bits for me (all previously know genericly as 'that bit there'). If you're up this way again then give us a ring and perhaps we can fit a cheekie pint in.
Kev
 
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