1990 Saab 900 Hatchback Logo
Posted on May 16, 2009
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Rough idle on 1990 saab 900 convertible, 16V

1990 Saab 900 16V turbo , 5 speed manual transmision

plugs & wires changed. Idle control valve changed. Air sensor cleaned, new air filter. Idle speed NOT adjusted.
alternator and battery replaced.
Synthetic oil, and all fluids checked

car idles in neutral around 900 rpms ( but sometimes you see a dip flux between 700-900 rpms... ) car motor has a bit of a shake

when car gets a little warm, when dropping out of gear to neutral, idle drops sharply to, or below 500 rpms, and stalls the car
can happed occasionally or some days it happens often...

what could be the problem

  • Anonymous Mar 19, 2014

    changed fuel pump, fuel filter, chip, air filter, oil, spark plugs, candles, not helped...

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3 Answers

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  • Expert 51 Answers
  • Posted on May 30, 2009
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Because the car has adaptive technology, it may take a while to reset and adjust to the new, cleaner and better conditions than those to which it had previously adapted.

Did you change the cap and rotor? if the plugs needed replacement, likely they do too

Possible other causes include:

loose or corroded connections to any electrical component you disturbed (make a checklist and tick them all off as you check them);

mis-reinstallation of any F.I. part disturbed(checklist again)

obstructed water flow through the AIC valve;

improper voltage output from the AIC valve (for LH 2.4 systems, should output 8 volt at idle, dropping as load increases; for LH 2.4.2 system output 7 volt at idle etc; testing between terminals)33 and 17 at disconnected LH connector;

possible problem with MAF.

Hope this helps

Saabreur







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  • Posted on Feb 20, 2013
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Sound like a vacume leak. it is old enough for then to start going bad

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  • Posted on Jul 08, 2009
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If nothing else works, make sure you haven't accidently disturbed the air pipes on top of the manifold, also it may need timing if it is shakey.

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