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Discussion Starter #1
1400-1700 ppm hc.if my cat. is no good it could reduce that to 140-170 ppm.ok.but still this indicates a lean mixture.dam.i've put in a 4 wire brand new O2 sensor.i tried a propane test on all the intake hoses and plenum and injector places. no increase in rpm.any idea out there what i should check? i'm thinking of hooking her up to the gas analyzer and playing with the tension on the afm.i don't know why that would change the high hc but i'm at my wits end.burn time is in specs tho at the short end.
 

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There is an idle bypass adjustment on the AFM (originally covered by a tamper-evident plug). This is used to fine tune the idle air allowed past the AFM to adjust the idle emmisions. Info in Step 12 of Greg's V-6 tune up & diagnosis page (link in my signature).
 

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thank you for your reply eric.but you see 1400-1700 ppm is not a fine adjustment.if you turn that plug all the way in you get a bit higher Co_Out you get air bypass and less CO.i'm not even sure if that translates at increased rpm.perhaps it does.but HC is another story.
 

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Discussion Starter #5
that is what i thought and tried to find at first.strangely enough i found in my bosch instruction book on l jetronic a large HC will be caused by a lean mixture.sort of goes against common sense.now i'll test all possible air leaks after the afm.it suggest spraying propane in likely spots and watching if the CO increases in your exhaust gas.i can only do that test after the cat. unfortunatly.
 
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