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  1. #1
    Saab Fan
    Join Date
    09 Mar 2011
    Location
    Guelph, Canada
    Posts
    33
    Saab(s)
    84 T8
    Thumbs Up:   0

    Cold good boost - warm poor boost

    84 900 T8. I just drove it over to a shop for a safety so I can get this thing on the road. I haven't driven it much since bringing it home 2 months ago. Just around the block.
    So when it's on warm up, it wants to boost like mad. As it warms up it boosts much less and you can feel the APC shutting it down.
    I have checked the fuel pressures and they are normal. It does need a cap, rotor, HT leads, plugs tune up.
    Any thoughts? It also idles up a bit around 1000. Intake leak? Injectors?

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  2. #2
    Paul A
    Saab Nut
    Join Date
    11 Mar 2011
    Location
    West London and Wiltshire, UK
    Posts
    251
    Saab(s)
    T16 '93 Ruby - T16 '94 Vert Ruby
    Thumbs Up:   0
    First thing I would check is if the timing is spot on, - not over advanced. It may boost more on warm up because the fuel mixture is richer and you don't have a hot engine.

    PS Console yourself with an 'Old Crow'.

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  3. #3
    Saab Fan
    Join Date
    09 Mar 2011
    Location
    Guelph, Canada
    Posts
    33
    Saab(s)
    84 T8
    Thumbs Up:   0
    Well I want to do the valve cover gasket and swap on a recently rebuilt distributor I have, so I'll set the timing up and do a full ignition tune up and we'll see.
    Just got word it passed safety!

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  4. #4
    Edward G
    Saab Enthusiast
    Join Date
    10 Mar 2011
    Location
    Victoria Australia
    Posts
    121
    Saab(s)
    T5.5 84 900T8
    Thumbs Up:   0
    Is yours intercooled?

    After ignition check injector spray pattern if you can be bothered. My injectors were stuffed, at $40 each new they're cheap and the difference was pretty astounding

    I'd also try turning the mixture screw 1/8th of a turn clockwise to richen it up a bit. My Saab mechanic said they ran a lot better at 1-1.5% CO than 0.15-0.5% as I think the Bentley/saab manual specifies. As you know on 8valves the mixture adjustment changes fuel delivery throughout throttle range.

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  5. #5
    Saab Fan
    Join Date
    09 Mar 2011
    Location
    Guelph, Canada
    Posts
    33
    Saab(s)
    84 T8
    Thumbs Up:   0
    Peva was correct. I drove it up to the farm (160km) and it definitely felt like it was advanced, especially the way it was fluttering out in the top end. So I earballed it till the rpm dropped to 850 or so and the tickover relaxed.
    Took it out for a blast and what a difference. I'll do the vc gasket and new ignition parts, set it with a timing gun, and I think it will feel pretty close to perfect.

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