[DML] Re: why does cold engine rev?

["David Teitelbaum" <jtrealty@xxxxxxxxxxxxx>]

It probably is not the O2 sensor. It takes a while before that system
 becomes active. More likely it is the thermistor for the high idle.
On most Deloreans it hardly functions at all. When cold it is supposed
to bump up the idle a a little till the motor warms up. Hunting (aka
surging) can be considered "normal" especially when cold. At least I
would not spend any time fixing it unless it is seriously affecting
cold drivability. I would not recommend modifying the O2 sensor to a
heated one. The system is not designed for it and heating up the O2
sensor will make the Lambda system start prematurely. The whole
warm-up cycle is designed for just the way it was built. If you heat 
up the O2 sensor you are going to have to warm the motor up faster and
change the operating curve for the Control Pressure Regulator. For
most it is best to leave things "stock". This could also be caused by
a problem in the vacuum advance circuit. Check your timing and the
condition and routing of the vacuum hoses.
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxxxxxx, Farrar Hudkins <fhudkins@...> wrote:
>
> Yes. That is the side effect of the oxygen sensor warming up. I have 
> known some owners to replace the sensor with a heated one and this
is no 
> longer a "problem." (In quotes because it's not really a problem anyway 
> -- mine stops revving when I put it in gear.)
> 
> Cheers,
> Farrar Hudkins
> #2613 (auto)
> 
> daviddelorean wrote:
> > 
> > 
> > After a cold night or after not using the car for a few days, when I
> > start the engine and let it warm up after a few minutes the car begins
> > to rev on its own. It goes through cycles where it revs at slightly
> > higher RPMs for a few minutes then it stops. Is this normal?
>




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