[DMCForum] Fuel mixture

["aaron_t_graham" <aaron_t_graham@xxxxxxxxx>]

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 
completely.

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 
mixture?

Thanks for any help you can give.
Aaron
#1506

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