Re: [DML] exhaust and idle
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Re: [DML] exhaust and idle


John, do you really adjust the mixture by feel alone?? If the answer is 
'yes' then I say that no wonder so many DeLoreans start and run poorly and 
have no power. You cannot do that by feel! You are right saying that a 
little bit goes a long way.. and if you would do it like it should be done 
by using a gas analyzer you'd know that 1/8 of an inch might take you from 
one limit to the other limit of the lambda circuit... meaning that it might 
take you from too lean for the lambda to work properly to too rich or vice 
versa. The frequency valve will still be buzzing all the time but it will be 
in the fixed "limp-home" mode running at 50% duty. All that means that the 
car will still run but it will be harder to start, might hesitate, will not 
develop full power and might use more gas. This is especially true for harsh 
weather - hot, cold, wet. My car starts every time in less than a second 
even after sitting for two months untouched... and regardles of weather or 
The ONLY way to properly set the mixture is by using a gas analyzer 
connected to the exhaust ports upstream of the catalytic converter. Another 
method, although not as good, that might still work is it to replace the O2 
sensor and set the mixture using a dwell meter connected to the frequency 
valve. In this case you need to set the mixture to the point where the dwell 
meter reads about 50% of the full swing at idle(note: not 50 on the scale, 
but 50% of the full swing regardless what numbers are printed on the dial). 
Plus you need to get it to a point where the dwell goes up and down and the 
reading is NOT steady 50%. It usually goes from 45 to 55%. If you get a 
steady reading that means you are outside the range of the lambda circuit 
and the mixture is not controlled by the ECU.
When adjusting it the way it should be done you will see that sometimes just 
'pressure' on the wrench might be enough to get it up or down by 10%. If you 
turn it by 1/8" you'll run out of the lambda range.
DO NOT DO IT BY FEEL!!!! Do it right

Tom Niemczewski
vin 6149 (in Poland!)
Google earth: 52°25'17.30"N 21° 1'58.00"E

----- Original Message ----- 

> Ed, Be sure when your adjusting the fuel mixture screw that a little bit
> goes a long way. What I do is insert the 3mm long handle wrench into the
> hole with the handle pointing at the 12Oclock position then make the small
> adjustments left for lean or clock to enrich, just do it in 1/8" steps.
> The frequency valve should buzz all the time. What it's doing is allowing
> fuel to return to the tank as told by the Lambda system.
> John Hervey

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