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Discussion Starter · #1 ·
Hi Saab Fans,

I got a Maptun Stage 3 97' 2.3FPT Auto. And here comes the boost dilemma;

Boost readings;
1. APC fuse connected; 1.3bar peak and sudden decrease to 0.8bar steady.
2. APC fuse disconnected; 1.4bar peak, 1.1bar steady and no overboost fuel-cut.
3. W port of APC diconnected; 1.35bar peak, 0.9bar steady and no overboost fuel-cut
4. W and C hoses connected, APC solenoid bypassed; 0.35bar peak/base all...
5. Vacuum; riding downhill at 3rd gear -0.75bar.
6. Vacuum; at idle 0.5bar.

During test ride, under any condition I have never experienced overboost fuel-cut (I guess there must be?).

PS.I also tried to check the base boost at 3rd gear (auto trans) with 3K rpm by lightly pressing brake but the boost did not come down to level to call namely base boost.

Which is the culprit; APC Solenoid? Wastegate Actuator? OR is there any other item I must check? Johnny from Maptun says there could be a leak somewhere. But where???

If I change the wastegate actuator to a stronger one such as 0.5bar could it be the cure?

Any suggestion welcome
 

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This is all very odd.

APC fuse removed (2) should be the same as C&W connected (4)

Also,

W disconnected (3) should be manic boost and overboost.

APC fuse connected (1) sounds about right but a bit low.

I wouldcheck the WGA is set stong enough, isn't pulling or blowing open. Also, that the wastegate itself isn't sticky and not shutting properly.

I think you need to get out with a multimeter and pressure tester and check all the hoses and components for pnumatic and electrical compliance.

Also, as all the items 1,2 and 3 that went via the APC solenoid gave 1.3 ish bar, it could be that the solenoid is bad and part welded shut (mine went fully shut last year...
)

Andrew
 

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I am leaning towards what Mark E has said, it's a faulty APC solenoid.
When I suspected my solenoid wasn't up to spec but was still working, I got the mechanic at the dealership to 'borrow' a new one from the store, on the basis that if there was an improvement in the boost, I'd buy it. What a difference it was!

Another thing I found out recently, if the ignition switch is 'ON' but you haven't started the engine, the solenoid should vibrate. If it doesn't, then you suspect the solenoid. I however assume this is true only for a complete failure of the valve.


Scaero wrote:
W disconnected (3) should be manic boost and overboost.[/b]
I am still disturbed that this is not happening.
 

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Discussion Starter · #5 ·
Thanks all for kind help.

I guess when I remove APC fuse or connect C&W hoses, the result is running base boost. Is it correct?

Today will check the wastegate and actuator, hopefully borrow an APC solenoid from service shop, thereafter a system pressure test will follow.

As Mark E indicates, I guess my APC solenoid could have a sticky operation together with a leaking WG & WGA operation. I guess if have to replace, a 0.5bar WGA will be fine.

Here comes another question; If APC is the culprit, should I merely replace the APC solenoid? Is it possible to clean/lubricate, service APC?

I'd post the results at once.

Have a good day!
 

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Discussion Starter · #6 ·
Going through the checklist generated by the contributors of this post, I have found that my WGA is very loose (can easily be pulled by hand) and APC solenoid has died..

Now, waiting for the replacement parts to come.

Thanks all of you!
 
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