Tuning 505 STI
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Thread: Tuning 505 STI

  1. #1
    Gus
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    Tuning 505 STI

    I just came into possession of two new gizmos for my 83 505 STI:

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    1) A new thermostat. Car no longer runs cool all the time(!)

    2) A digital tachometer (part of a multimeter)

    According to the digitial tacho, it's idling ~ 650rpm when warm which isn't good at all. The engine revs fine, but if the throttle is suddenly released the revs drop rapidly, threaten to stall, then return to 650rpm.

    The Haynes manual describes a method for setting the mixture on a K-Jetronic for people w/o access to an emissions sensor. Can anyone vouch for this method's effectiveness or should I take it to the professionals? (Budget alert: I'm a uni student!)

    I have a niggling feeling that while it may be bad now, adjusting it may make it worse .

    Also, the timing is slightly retarded. Will this effect idle or just power?

    Oh, and I've found the mixture screw (it's under the conical tube-like cover, in front of the airflow meter, right?) but I can't find the idle screw - where is it?

    For the record, the extra air device works properly and so does the cold start injector.

  2. #2
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    Hey gus.
    STI injection mixture setting is VERY sensitive.The idle speed is easy though.Look carefully down the passenger side of the inlet manifold.Under the big aluminium chamber sit's a black knob about 25mm diameter.Turn this out to speed up the engine.The idle speed drop's if the timeing is retarded(the technical stuff we won't worry about).Hope this help's. dance

  3. #3
    con
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    Gus,

    I would be very wary of trying to adjust air flow etc. on the Kjet if you don't know what you're doing: most times it will get worse and it gets very expensive if you make a mistake. I agree with Chuck, stick to playing round with the idle speed knob. Your idle is set too low; should be 900-950rpm.
    For general tuning, the things you can do yourself is replace things like:
    - fuel filter (every 30,000km - when was yours changed?)
    - check the timing (with vacuum adv. disconnected)
    - spark plugs
    - new HT leads
    - every so often put a can of good quality (eg.Techtron) fuel injector cleaner into a full tank

    good luck

    con.....

  4. #4
    con
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    Gus,

    If you are still determined; there is a way of adjusting the idle speed mixture w/o an exhaust gas analyser. The procedure is described in the official Peugeot workshop manual.
    I can fax you the page.

    con....

  5. #5
    Gus
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    Hmm... well, some time ago I took off the air flow plate cleaned it, and re-seated it. This caused one of the mechanics I know at Alpine Motors to drop his jaw, but I think it was justified as the plate was both filthy and grating against the air flow housing. After about 30 minutes with a feeler blade I felt I had it more or less re-centred (Although I haven't checked how it's progressing.)

    Anyhow, what I _meant_ to say is. The process described in Haynes is:

    "To adjust the mixture without using an exhaust gas analyser, turn the air adjustment screw to obtain an idle speed 50 rpm above the specified speed. Turn the mixture screw to obtain the maximum engine speed, then re-adjust the air screw to obtain the original speed. Now unscrew the mixture screw to obtain the specified idle speed."

    Does this differ from the method described by Peugeot?

    (I'll try just adjusting the idle tomorrow morning and that will probably be all I'll do as - as I said - the engine revs fine and runs fine at speed.)

    While we're talking tuning, though, the awful positioning of the distributor has me thinking about building and installing Jaycar's Programmable Ignition Kit (which also requires their electronic ignition kit), allowing timing changes, etc. on the fly (and removing the need to play with the distributor.) Has anyone tried this, or know anything about it?

  6. #6
    Tadpole
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    May i suggest if you do want to attempt the gas analyzer methed see if your local club has one in their tool library. I know the Victorian one does and as a student myself the money to join easily pays for itself

  7. #7
    Gus
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    Of course!! The ACT club mechanic is in Europe at the moment but I'll track down the guy who's standing in for him and see if we have an exhaust gas meter.

    In other news: I loosened the idle screw a lot (probably 10 full turns if not more) this morning and pulled the revs when warm up to about 880-900rpm, but I'm aware this is probably _way_ too much of an adjustment for this to be the actual problem.

    I'm going to do:

    - air filter (i was gonna do it next week anyhow),
    -new spark plugs (running cold all the time may have coked the whole head and the plugs don't look too great although they're only six weeks or so old),

    - clean the throttle body (maybe even take the whole plenum off the car),

    - check the idle switch on the throttle is working (I checked it with my multimeter this morning but I'd like to be sure),

    - check the air flow sensor plate still moves freely...

    - check the timing is at least roughly correct.

    Anything else I should be doing? (I guess I should check fuel flow - or pressure if I can do so - while I'm at it, and put some injector cleaner in when I get a chance. Although both fuel pump - last year - and fuel filter - last month - are new so I doubt it's a fuel flow problem. That and the car revs OK.)

    I guess the most important thing is to make sure that, whatever I do, I don't make anything worse.

  8. #8
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    Gus,
    I suggest a set of o ring's at the injectors and their plastic mounts.Clean the throttle internally
    useing spray carby clean.Finaly STI's have alway's got air leak's on the hoses for the auxillary air valve and other joint's which you fix with hose clamp's.Fix those and you should have a better idle adj.

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