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Discussion Starter · #1 ·
Hi Everybody.
After doing a search for the problem I didnt find anything that was quite the same so here goes with my question.

Car: 1991 CS 9000 2.3 Turbo Manual. 128k

Recently, the car would hesitate on anything more than 50% throttle. As the boost increased into the red the car would back off, then increase again. The cycle continued.

After various checks of hoses, plugs etc I spoke to a saab 'expert' who told me that it was almost certainly the APC solenoid that sits on the right side of the radiator.

I sourced another APC solenoid to try. The first one (second hand) I received gave the same symptoms so another was sent to me which was also second hand.

This one however appeared to have cured the hesitation under full throttle however it seems that I am not running more than base boost. 50%-75% in the yellow region on the standard gauge.
This boost remains the same whether the ECU is attached to the APC solenoid or not.

I have checked that the rod connecting wastegate and actuator is connected and it moves freely and springs back into place. Which it does.

Someone told me that i can check if the wastegate is operating correctly simply by sucking the hose that leads up to the APC solenoid is this correct?

Sorry for the long post.

Any advise or suggestions would be very greatfully received.

Thanks guys

Brett
 

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Welcome to Saabscene

The resistance values look OK, so I would guess it's not the solenoid.

That leaves a couple of other possibilities- a vacuum hose leak somewhere, a faulty wastegate actuator, or a failing DI cartridge. To eliminate the latter, simply substitute it with a known good one.

To eliminate the actuator, disconnect the middle (W) hose from the APC solenoid, then go for a drive. On a suitable uphill stretch of road, try gently accelerating from around 40mph in 3rd. The boost should rise nice and steadily. Be aware that of you give it too much, the overboost protection will cut in, which is very sudden and severe.
 

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Discussion Starter · #5 ·
Bubbles.

Just come back from performing your test.

Boost rises steadily and gives good acceleration.

Gauge needle well into the red wheras with 'W' connected the gauge goes to a maximum of 3/4 of yellow. I hope you know what I mean by this.

So does this emiliminate actuator/wastegate problem?

Does this just leave a vacuum hose leak or a failing DI cassette?

Thanks again for your help.
 

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Discussion Starter · #6 ·
I have just checked the voltages across the pins on the ECU cable which connects to the APC solenoid, they are as follows:
Ignition key on but engine off.

1-2: 12.1
2-3: 2.1

Is this low voltage across 2-3 a problem.

Also, I have re-tried one of the old APC solenoids and I get good boost but the car hesitates and jolts under severe acceleration as before whereas this APC solenoid does not jolt or hesitate but also does not allow boost properly.

Also, on the solenoid I can blow air through 'C' and it escapes through 'W' and also the other way around but 'R' seems to be blocked. Is this normal?

Any thoughts anybody?

Thanks
 

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Discussion Starter · #7 ·
Billy no mates here replying to my own posts.

I have just found this from another post from PAulM

'I had the same problem on my Aero recently. It was a failed APC solenoid valve as LocoSaab has suggested. However, mine was fine electrically, but had failed internally; the small metal disc inside had broken into 3 pieces and sealed the R port, leaving the C (compressor?) port permanently connected to the W (wastegate) port. This results in base boost only. '

Have I just found the source of my probelm (the lack of boost not the lack of mates!) ?
 

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Discussion Starter · #10 ·
Hi Paul

The symptom that I had was engine hesitation and cutting out under hard acceleration. Which was apparently overboost protection working, I'm just quoting the expert here.

They have just ruled out MAF sensor, APC solenoid and they have now replaced the DI cassette and all is well and the car is going well.

It was probably my poor terminology that has confused. or is this not the case?

Could the symptom that I was having never be attributable to a faulty DI?
I ask with dread, in case they are pulling a fast one?? (the garage im using (for the first time)seems really good so i doubt that very much)

Cheers

Brett
 

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Cutting out and hesitation under acceleartion, is a typical DI symptom. (NB: Sometimes they fail intermittently like this, other times they fail 100%, in which case you might just notice a whiff of smoke - if your quick enough - and a lingering smell of burnt oil).

But the intermittent DI fault is not an overboost fault.

Sounds like the garage was using the wrong terminology.

Overboost will result in a sudden cut in power, when the overboost protection cuts in. As others have reported, this is quite harsh. If the overboost sensor was playing up, it would not be a DI problem.
 

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Hey 9k, I am trying to understand the problem you had. In my 94 CDE FPT, the gauge only goes about 50-70 percent into the yellow. I will try disconnecting the middle hose and report back. What fixed your problem? My DI cass. is about a year old! And input is good input.
 

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Discussion Starter · #14 ·
Saabeh

Hello mate.

The symptoms that I had are pretty much as my first post describes.

Under hard acceleration I would get a misfire and the boost would increase into the red section of the gauge but rapidly back off into nothing more that about 3/4 of the yellow. I could however accelerate very gradually without the misfire.

Lots of things were checked, APC solenoid, spark plugs, MAF sensor but the fault was found to be the DI cartridge. The garage replaced this and the car now runs very well. Apart from a minor problem with excessive fuel consumption (although my recent ECU reset and adaptation run seems to have helped, see other post if interested).

Are you experiencing just a lack of boost? ie. the boost gauge not going any further than mid yellow? If this is the case do a quick search on here to find several posts with these symptoms.

A lot of knowledgable and helpful people on here.

Good luck with getting your boost problem resolved.

Cheers
9k
 
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