Re: [DMCForum] Fuel mixture
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Re: [DMCForum] Fuel mixture

Let's start by taking it to the point where it idles nicely with the
frequency valve buzzing when the car's warm. Now when you do a cold
start and it's idling like a bag of nails, priess the full throttle
microswitch. Does it run better?

If so: Lambda thermal switch is bad and the lambda system is constantly
in "warm" mode meaning when cold, the engine's all over the place
because the lambda sensor will be giving bad readings - poss making it
far too lean as you suspect.

An over-rich adjustment on the mixture screw will not make much
difference when the car's accellerating.

What do you mean by "Once the CPR shuts off, the exhaust quiets down,
and the engine runs smooth.It still hesitates and jerks occasionally
until it warms up completely."

Specifically about the CPR shutting off?


aaron_t_graham wrote:

>I've been trying to get my fuel mixture just right over the last week
>or so.  Does anyone have advice for me on how to go about this the
>right way?  Here are some observations/assumptions/questions:
>1) If I turn the air mixture screw far enough in the clockwise
>direction, the engine starts hunting terribly during idle.  However,
>the engine seems fine when it's not idling -- very smooth operation,
>warm-up phase is good.  The frequency valve stops buzzing.  Does that
>mean the mixture is too rich?
>2) If I turn the screw counter-clockwise, the car gets to a point
>where it runs awful during warm-up (before the 40-deg C point).
>3) If I keep turning it counter-clockwise, it eventually stops
>hunting and the frequency valve starts buzzing again.  However, by
>this point, the initial engine warm-up phase is painful: the engine
>misfires, hesitates and jerks during acceleration, I have to press
>the gas pedal down further, and the exhaust is MUCH louder.  Once the
>CPR shuts off, the exhaust quiets down, and the engine runs smooth. 
>It still hesitates and jerks occasionally until it warms up
>4) I've tried two different CPRs on this engine and the one I have is
>good.  If there's a problem with the CPR, then it's due to a vacuum
>leak.  But I have looked for vacuum leaks and haven't found any.
>5) It doesn't make sense to me, if the mixture is lean, that the
>engine would run worse during warm-up, since the mixture is generally
>richer during warm-up than at other times.  Wouldn't this be an
>indication that the mixture setting is too rich?  Can someone explain
>to me why this isn't the case?
>6) Is there a good way to set the mixture correctly without using a
>CO tester?  What's the best indication that I have the correct
>Thanks for any help you can give.
>Yahoo! Groups Links


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