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  1. #31
    Hear my Saab a comin' nuclear944's Avatar
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    19 Dec 2010
    Location
    Bulgaria - Eastern Europe
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    95
    Saab(s)
    Past: 1989 SPG & 1989 900 N/A Sedan
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    Well I've always put 87 at the very least and I recently tried using 90 but no noticeable change in drivability occurred except for mildly increased power.

    It is definitely running lean under load and rich for the first minute of a cold start.
    Like I mentioned before, swapping the AMM with the turbo one made the vibration disappear. It's not an illusion. I am certain.
    I will list once again what I've done:
    -cleaned and tightened all grounds I had access to
    -changed distributor cap
    -did a compression test, which seemed to be successful
    -swapped AIC which didn't make a difference
    -adjusted TPS
    -checked for vacuum leaks very thoroughly

    There was a clacking sound on starting in 1st before, but after regapping and changing the spark plugs, it no longer does it.
    I had a person do 1st gear starts while I was watching outside and the engine doesn't audibly "knock" or "ping".
    Therefore, I can't tell if it's actually knocking (detonating/preigniting).

    It just vibrates a lot on load. It is running lean. It's obvious. Upon sudden throttle application, the engine hesitates for a fraction of a second.

    Maybe I should leave this thread for a while until I manage to change the fuel filter. I have tried to unbolt the banjos a couple of times with no luck...

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  2. #32
    Hear my Saab a comin' nuclear944's Avatar
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    19 Dec 2010
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    Bulgaria - Eastern Europe
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    95
    Saab(s)
    Past: 1989 SPG & 1989 900 N/A Sedan
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    New question:
    Since I cannot find any 89 fuel ECU's, is there anything else that could fit? I am really confused about the different versions of the ecu's and such.
    Also what is the actual problem with the 89 ECU? Is it a poor connection? Incorrect capacitors/electrical components? I am competent with soldering.

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  3. #33
    Edward G
    Saab Enthusiast
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    10 Mar 2011
    Location
    Victoria Australia
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    121
    Saab(s)
    T5.5 84 900T8
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    Hey Nuke

    This is a bit of a random thing to look towards but perhaps you need to get your injectors ultrasonically cleaned, have they ever been cleaned before? Definitely change that fuel filter if it hasn't been done before! GET STUCK INTO IT

    I'll explain why I think this, if your car has rough idle when cold and smells fuelly this could be because your injectors are dirty or clogged. When the engine is cold the ECU enriches the mixture, this is obviously achieved by increasing fuel volume to injectors... IF you increase fuel volume then you need to have sufficient flow and minimal resistance for the volume to reach the cylinders, in addition to this if you increase the fuel volume there must be excellent atomization of the fuel for ignition (obviously if your increasing the amount of fuel, it will need to retain a quality of atomization to ignite) If however you have clogged injectors the fuel will not be atomizing as well as it should resulting in dribbling or thicker stream, this can affect combustion and prevent it occurring reliably, resulting in rough idle and fuelly smell (as unburnt fuel that was unable to be combusted due to poor atomization is ejected from cylinder on exhaust stroke). The reason this would go away after warm up would be as engine warms up ECU leans off mixture and so at idle there is a reduced volume of fuel flowing through injectors and less stress on atomization of the fuel or less quantities of poorly atomized fuel being present to have a negative effect on combustion. However dirty or clogged injectors will have significant consequences when an engine is under load, and can produce driveability problems such as hesitation of varying degrees and a distinct feeling of less power.

    I am saying this because I had this problem, My car would run horrendously when cold, it would get better at idle once engine was warm but then still drive like crap if i was accelerating out through the gears. I replaced my injectors (mechical injectors as ultrasonic cleaning is not effective) and the difference was unbelievable...

    Perhaps it's worth doing if never done before, It is expensive, but if you replace the fuel filter and then do it, you won't have to get them cleaned again for another 20 years!

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    Last edited by s900t8v; 12 March 2011 at 07:07.

  4. #34
    Sam Carlson
    Tutorial Bot euromobile900's Avatar
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    14 Aug 2010
    Location
    Medford, MA
    Posts
    683
    Saab(s)
    '90 900 LPT with a flat-nose conversion
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    Quote Originally Posted by nuclear944 View Post
    New question:
    Since I cannot find any 89 fuel ECU's, is there anything else that could fit? I am really confused about the different versions of the ecu's and such.
    Don't you have two '89s? Try swapping 'em, just for the hell of it.
    Also what is the actual problem with the 89 ECU? Is it a poor connection? Incorrect capacitors/electrical components? I am competent with soldering.
    I wish I knew.

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    Ask me a question about your c900! I promise I either can answer it or know someone who can

  5. #35
    Edward G
    Saab Enthusiast
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    10 Mar 2011
    Location
    Victoria Australia
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    121
    Saab(s)
    T5.5 84 900T8
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    Regarding the ECU's Nuke, my Mums car had a bad ECU it would run terribly rich and then spontaneously solve itself, I believe that this would occur once the circuit board heated up a bit it would flex and the connections would become stable again, however the thing in the end that stopped the ECU from working all together were bulging capacitors... If your competent at soldering and know what bad caps or cracked or fatigued joints look like then you should definitely pull your ECU apart and have a squizz!

    We replaced the capacitors with those of the same rating and the ECU worked fine again in my mums 900i

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