[DMCForum] Re: Hot Start Fixed? (Vacuum Leak)

["content22207" <brobertson@xxxxxxxxxxxx>]

Fuel mixture is determined by metering piston raised by the air sensor
plate. Doesn't matter which route air uses to enter the engine after
that. Any route will do, so long as it does not bypass the air sensor
plate.

Cold start tube (next stop after idle speed motor) goes the same place
as throttle plates->U pipes->intake rails. It feeds centralized air
passages inside the intake manifold that exit right at the intake
ports (look for them next time you have your intake manifold off).
Over the throttle plates or through the idle speed motor, air ends up
at the same place.

Consider this: people idling off the brass manifold screws in lieu of
CIS (how every PRV operated before 1981, and Renault long thereafter)
can not open & close them on the move. Those air passages are opened a
set amount all the time. They have to be, or else the engine won't run
(after aux air valve closes, unless throttle plates are cracked). Same
difference as an idle speed motor stuck open.

Bill Robertson
#5939

>--- In DMCForum@xxxxxxxxxxxxxxx, Samuel <samuel_yahoo@xxxx> wrote:
> Ok then, what do you get when you have air coming thru the idle speed 
> motor, while not at idle, but have the throttle plates turned due to 
> pushing on the accelerator? I viewed it in the sensce of more air into 
> the engine than there shuld be due to the throttle plates controling
the 
> amount of air into the engine to be mixed with the gas injected via the 
> air plate.
> 
> Did it result in an over rich of the mixture? I know the end result was 
> the engine almost stalling due to pressing on the accelerator and 
> disabling the idle speed switch but still having air flow thru the idle 
> speed motor.
> 
> Samuel
> 
> content22207 wrote:
> 
> >Idle speed motor can not cause a lean mixture (unless it's leaking air
> >from the outside world). Only unmetered air can cause a lean mixture
> >-- like a vacuum leak. The idle speed motor serves the same purpose as
> >(variably) cracking open the throttle plates. Follow the path of air:
> >over the air sensor plate, through the motor, into the engine.
> >Identical to throttle plates: over the air sensor plates, through the
> >throttle plates, into the engine. Also identical to the brass manifold
> >screws BTW: over the air sensor plate, through the air passages, into
> >the engine. Notice the common theme -- over the air sensor plate. Only
> >air bypassing the air sensor plate causes a lean mixture: leaking
> >manifold O rings, leaking U pipe gaskets, leaking vacuum hoses, etc.
> >
> >PCV is the only exception.
> >
> >Look at the pic of my BBQ'd spark plugs in #5939's DML photo album if
> >you want to see what a lean mixture looks like... (cracked vacuum line
> >to my HVAC mode switch did that).
> >
> >Bill Robertson
> >#5939
> >
> >  
> >
> >>--- In DMCForum@xxxxxxxxxxxxxxx, Samuel <samuel_yahoo@xxxx> wrote:
> >>I have been tracing down a hot start issue and running issues on
my car 
> >>for a year now. I stumbled across a few things that was giving me 
> >>trouble today, with help from Walter.
> >>
> >>Figured out that my idle speed motor was stuck 1/2 way open. As a 
> >>result, I would be running fine at idle, but then hit the gas and
would 
> >>run too lean, almost stalling the engine. There is question about my 
> >>oxygen sensor, although the readings appear fine. The other is
that my 
> >>thermotime switch was bad. This would result in my cold start valve 
> >>running when the engine was warm. The end result was flooding the
> >>    
> >>
> >engine.
> >  
> >
> >>Hopefully, I'll have the engine running without the hotstart, as a 
> >>result, I'll be able to drive and actually get other projects done on 
> >>the car, like getting my interior back in.
> >>
> >>
> >>Samuel
> >>#5096
> >>    
> >>
> >
> >
> >
> >
> >
> >
> > 
> >Yahoo! Groups Links
> >
> >
> >
> > 
> >
> >
> >
> >
> >
> >  
> >

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