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Hi, I was just driving home from work and when I pulled out into the street and accelerated i didnt get any power at all, it was almost like being in neuteral. I then floored it and still no power, I could hear the turbo blowing, but the apc gauge was only half way in the orange. Normally the apc will just touch the red, so clearly the apc/ some computer system is limiting the turbo. I also noticed that when this was happening there was an extremely loud tapping noise comming from the engine, which got me really scared. Its like the sound that the engine makes wehn i first start it before the hydrolic lifters turn on, like the tapping of the valves (metalic tapping noise). It seemed like my car was in some type of limp home mode but then after about 10 minutes on the road the tapping noise went away, and I gained full boost and it ran normally. I am afraid to drive it now because i dont want to hurt it:cry: :cry: so can anyone please help me figure out whats wrong with my baby :cry:

Tommy
 

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Sounds like detonation (also known as knock, pinging, or in the UK pinking which is closest to the actual sound you hear). Occasionally, for no apparent reason the knock sensor and APC system or the Trionic system, depending upon the model year, allow inappropriate boost which results in knocking. This should go away quickly. if it doesn't then you need to have your APC solenoid (APC system) or BPC solenoid (Trionic) checked. Possibly the base boost is wrong or the hose to the wastegate is leaking. Or you had some very bad gas.


Bottom line is if it happens repeatedly you need to get the boost sytem checked out. if it happens only very occasionally, get better gas and try not to worry about it. One tip, if you get knocking do not floor it, you just make it worse. Which reminds me if you have an APC car you have a vacuum retard distributor which could have a leaking vacuum hose which would lead to incorrect timing under boost. If the timing is off by enough you can also get knocking. The vacuum line on these distributors retard the timing aggressively when the engine goes on boost. If this doesn't happen you can get bad knocking before the APC can react.
 

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I forgot to mention that the tapping noise didnt stop when i took my foot of the gas and idled it. If what you said above was true then the tapping would only happen when the turbo is boosting, am i right? Do you still think its the apc?
Thx
 

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Could be any number of Things..not that that helps much, Does yr Model still Have APC? I can't remember fer sure.
On a personal note: keep V far away From Swedish Auto... I've seen their Bungles on a LOT of cars.
 

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For info: S.A.'s owner/mech is not a Saab master tech ......

Good luck, Tommy !


Basre said:
Could be any number of Things..not that that helps much, Does yr Model still Have APC? I can't remember fer sure.
On a personal note: keep V far away From Swedish Auto... I've seen their Bungles on a LOT of cars.
 

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90 is APC I believe. Tapping at idle would probably not be ignition timing nor would it involve the boost circuit.


Need more information I guess.
 
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