K Jet tuning

H

Haakon

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Fellow Frogger
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May 12, 2002
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This bloody thing is doing my head in... Cannot get this bloody STi to idle smoothly. Have done plugs and leads (assuming the timing is right though - it should never need to be adjusted right?) and endlessly played with the mixture screw on the fuel distributor. Replaced idle air valve, fuel distributor and control pressure regulaotrs with no effect.
I have got it running really well whilst driving, fairly economical and idling very nicely in neutral BUT it just wont idle smoothly in drive. Cant get the idle mixture to any point of smoothness with that little bit of load on it.
HELP!!! What am I missing? The motor is no spring chicken (230K km) and blows a little blue smoke when cold - am I wasting my time until it gets new rings?
Both my R25 and R21 with the douvrin motor have these sort of Ks and behave perfectly (albeit with a better efi setup), as did a Fuego with even more Ks on it. I just cant believe there is nothing to be done - I know its a pretty primative injection system, but my LTi 504 had an even more primitive one on it and it idled in drive fine with 300K km on it.
 
experimented with timing for the hell of it, and it now idles much nicer with the timing retarded a couple of degrees, with no noticible performance drop. :dance: God I love computer controlled EFI - it does all this sort of stuff for me....
 
Alpine Motors once retarded the timing on my K-Jet 505 and it improved the idle as well (I always resented it cos I figured I'd lose power, but in that case maybe not.)

Have you cleaned the air flow plate and made sure it moves properly? Mine was off-centre and scraping against the "cone" for a while, and it helped throttle response when I took it off, cleaned it, and re-centred it with a feeler gauge (fiddly job.)

The other thing you could do is check for tiny vacuum leaks. Easiest way I know is to get a spray bottle of water and slowly spray it on all the joins with the motor running, listening/watching for water being sucked in. Check Injector O-Rings thus, too.
 
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