Re: [DML] VIN#04421 Lives Again and Rough Idle - Vacuum Leak
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Re: [DML] VIN#04421 Lives Again and Rough Idle - Vacuum Leak


An update on cold start rough idle troubleshoot.  Hopefully these data
will help other D owners.

The idle speed motor micro switch resistance values are: 0.3 Ohm
closed.  27.8 Ohm open circuit.  Values were checked 3 times.  Proves:
micro switch is working.

With the electrical connection to the idle speed motor disconnected
and not depressing the gas pedal, the engine will crank and flood.
(Bad!!)  With the connection reconnected, engine will start just fine.
 Proves: idle speed motor is working (but correctly? don't know).

Liberal amount of WD-40 on all vacuum hose lines doesn't change engine
speed at all.  Proves: nothing.  The more pontent gas - propane, is
the next logical choice.

Took a 3mm hex wrench and turned fuel mixture screw 15-20 degrees
counterclockwise eliminated the exhaust smoke.  Proves: crossing your
finger when turning the fuel mixture screw works.  Be sure to know
which direction you're turning it.

Hooked up an analog dwell meter to monitor pin 2-3 of the diagnostic
socket yields 30 to 35 degrees deflection on 6 cycle engine scale. 
According to the workshop manual, it should read 40-50 degrees. 
Proves: the mixture is either too lean or too rich.  See above
corrective action.

Dwell meter hooked up to pin 1-2 and pin 4-3 doesn't produce any
readings.  How does one check the RPM with a meter?  What components
to hook up to?  My dwell meter also has an RPM mode which I can use.
Proves: I don't know what the hell I am doing. ;)  



--- In dmcnews@xxxxxxxxxxxxxxx, Warren Wallingford <warren@...> wrote:
> I did a long post last year, (I think), on vacuum leaks.  I concur with 
> your diagnosis.  An easy and fairly safe method of tracking down air 
> leaks is with a spray can of WD-40.  With the engine running, squirt
> oil on or near the place that might be leaking.  If the idle picks up 
> and smoothes out for a second, you've found one.  WD-40 is flammable
> not as volitile as gasoline.  I've used carb cleaner before, but 
> processing that thru the engine sends hydrocloric acid vapor out the 
> exhaust.  Usual suspects are: intake manifold, injector seals, w-pipe 
> gaskets, and especially the idle tube and associated piping.  You can 
> spray WD around pretty liberally without hurting anything, but keep 
> ----snip----

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