Re: [DML] Idle Speed

["content22207" <brobertson@xxxx>]

PRV *IS* extremely vacuum sensitive. Trust me. Test spray your
*ENTIRE* block, including oil pan, front and back, with carb cleaner
and you'll find leaks in places you never expected. Plus is great way
to clean off all that oil & other detrius. Are access covers for cam
bearings and vacuum take offs on backside of engine so don't neglect
there. I make extensions for the tube from tiny size vacuum hose to
better reach such places. Don't forget to check mating surface of cold
start tube, idle speed motor take off, and two vacuum take offs under
upper air assembly. Stick hose into dead space under intake manifold
to test ported vacuum switch and bottom side of intake O rings. 

To isolate vacuum leaks from misbehaving idle speed system I'd
recommend temporarily disabling it. eMail me direct for copy of
procedure: brobertson(at)carolina.net. You might find you prefer car
without it. IMHO system does not age well. Even purists have to agree
that ability to run engine manually is important diagnostic tool if
nothing else.

Was thread some time ago about endemic DeLorean idle speed wandering.
I disagree completely. Properly tuned and tight engine should idle
100% smooth and constant, idle speed motor and Lamda notwithstanding
(even more so without them!). Mine is ALMOST there -- think a new
timing chain cover seal for crank shaft will do it. Then #5939 will
FINALLY idle like a Lincoln...

Did you see John Hervey's post Re: vacuum leak through oil dip stick?
Is true, believe it or not (try it on a running tight engine).
Darndest thing I've ever seen...

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "John Hervey" <john@xxxx> wrote:
> Dave,
> Did you know that the oil dip stick is supposed to be sealed as best
you can
> down into the holder. Potential vacuum leak also.
> The idle speed motor can be tested by putting a 12 volt common wire
on the
> center conductor and then touch the red wire or hot to one of the other
> terminals. Then you can see the valve inside opening and closing.
> It's better you take it off to do the test.
> John Hervey
> www.specialTauto.com
> 
> 
> -----Original Message-----
> From: doctorDHD@xxxx [mailto:doctorDHD@xxxx]
> Sent: Friday, July 18, 2003 6:41 AM
> To: dmcnews@xxxxxxxxxxxxxxx
> Subject: [DML] Idle Speed
> 
> 
> I had a small oil leak, that seemed to be coming from the right side
valve
> cover gasket so I cleaned off all the oil and tightened a few valve
cover
> gaskets. The leak seemed worse but the valve cover gasket was dry.
The oil
> was
> coming from a "hole" in the upper left hand side of the right timing
chain
> cover.
> I quickly figured out that this "hole" was for bolt that I was
missing ever
> since I bought the car last October! I put a bolt in, snugged it
down and
> viola, no more leak. I drove the car and notice something very
interesting.
> It
> now idled smoothly at the 750 rpm it was supposed to. I was
ecstatic. So
> all
> this stuff about the DeLorean PRV being so sensitive to any vacuum
leaks was
> true I said to myself. When I got the car home the leak was fixed
but while
> the engine was running I touched the wires going to the idle speed
motor and
> all of a sudden the idle speed came back up to its previous state of
rolling
> up
> and down between 950 and 1200. It idles fine with the idle speed motor
> disconnected. Is this a bad ECU? What is the best way to trouble shoot
> this?
> 
> Dave & 6530