RE: [DML] Dwell meter readings + possible vacuum leak

["Joseph Kuchan" <josephkuchan@xxxxxxxxxxx>]

The FV is under control of the lambda ECU and just obeys "orders". It is the 
control element of the system while the lambda probe is the sensing element.

How old is the lambda probe, and how many miles are on it? Have you see the 
tip? Is it sooted up, oily, or clean? The unheated lambda probes used in 
DeLorean's must be fairly hot to operate. It sounds like your's may be 
drifting slowly in and out of operating range. This can happen easily at 
idle with a marginal probe as exhust temps are fairly low at idle. I would 
inspect and tess, or simply outright replace any suspect probe.

It can be monitored/tested in circuit using a high impedance voltmeter. If 
you can, put a high impedance voltmeter set to the 1 volt scale on it while 
the car is running and let us know what it happening. Does the voltage 
switch cleanly back and forth, or is it "stuck" at one reading. If it seems 
stuck, what voltage do you see? Or, is it simply drifting around?

Do whatever you can to pinpoint that hissing sound and report where it is. 
You need to find the noise because it is not normal and needs to be dealt 
with.

-Joe Kuchan

>From: "valleyrat12" <valleyrat12@xxxxxxxxx>
>Reply-To: dmcnews@xxxxxxxxxxxxxxx
>To: dmcnews@xxxxxxxxxxxxxxx
>Subject: [DML] Dwell meter readings + possible vacuum leak
>Date: Mon, 06 Mar 2006 05:36:32 -0000
>
>Ok here are my dwell meter readings. My Dwell meter is of the
>variety that has a + and - lead and then the dwell lead. I have
>attached the positive lead to the jump post and the negative lead to
>block. The dwell lead is connected to the orange wire that would
>normally be plugged into the diagnostic plug. This lead is melted
>and can not be plugged into the diagnostic plug.
>
>Fixed: 61%
>WOT engaged: 66%
>
>Then after about five minutes the meter goes from 61% slowly to 42%
>and then pops back to 61% and repeats over and over until it starts
>to settle at: 55%-44% so 50.5% average
>
>Fully warmed up: 58% - 46% so 52% average
>
>I can not get the meter to fluctuate around 45%.  Further enrichment
>causes the FV to stop buzzing and the dwell meter reading ceases to
>fluctuate.
>
>
>Now; I can hear this hissing sound on the driver's side of the
>engine. Listening through a piece of PVC pipe the sound seems to
>come from the hose that runs between the cold start valve and the
>idle regulator.  I removed the hose and it is fine but the sound
>persists! I originally though that the leak was coming from the tube
>that runs into the mixture control unit. Any ideas? I am assuming
>this is a vacuum leak but perhaps it's something else. Thoughts,
>comments, corrections, criticisms greatly appreciated.
>
>Nathan
>
>2277
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