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AFR 20%

Discussion in 'Technical Q&A' started by smooothchrome, Jul 26, 2006.

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  1. smooothchrome

    smooothchrome Rookie

    Jul 26, 2006
    1
    #1 smooothchrome, Jul 26, 2006
    I have a 328 bosch fuel injection. Well it's really not mine. The brother inlaws. Ive been a tech for ever but I have not had the pleasure of melding with this system (Yes ,that is sarcasm) so I'm hopeing someone can school me. The symptom is this: While I accelerate the AFR goes super lean like 20%. The car sputters and starves for fuel. At idle AFR is at 12.9%. Idles fine. Fuel pressure before the fuel dist. is 100psi . after the dist (to the injectors) is about 45 psi. I removed the exhaust because it felt as if there was a restriction. That didn't help. When the car is stone cold it runs terrific. I don't want to admit defeat to this guy . Any ideas?
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,932
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Jul 26, 2006
    Not trying to be critical, but I think that would be better expressed as 20:1 and 12.9:1 for the AFRs (not %).

    What version 328? A US K-Jet with Lambda or a Euro K-Jet without Lambda?

    If it's a US version 328:

    1. Is the metering valve (aka frequency valve) buzzing when the engine is running? (It should be whether warm or cold)

    2. Is that 12.9:1 AFR at idle with the O2 sensor unplugged or plugged in? Does it change unplugged vs plugged in? (and please confirm that you are measuring this upstream of the cat)

    3. If you unplug the O2 sensor, is warm running improved/unchanged/disimproved?
     
  3. snj5

    snj5 F1 World Champ

    Feb 22, 2003
    10,213
    San Antonio
    Full Name:
    Russ Turner
    #3 snj5, Jul 26, 2006
    Last edited by a moderator: Sep 7, 2017
    From dynos I have seen, the 328s pull dang close to stoich. (14.7) throughout the range

    In addition to Steve's pointing out checking the frequency valve, going lean under load in a K-ketronic could very well mean restricted fuel flow or pressure. That is, I'd replace the fuel filter and ensure the pump is not in failure.

    Something similar also happened to me with the failure of the O2 sensor protection relay (the one with the fuse in it). It's in the trunk on a Mondial 3,2. but maybe in the passenger footwell on a 328.

    good luck!
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