RE: [DML] Is My Idle OK?

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

Todd, 
Try doing this by ear as you say find the sweet spot. Get the car hot and
unplug the 02 sensor. Adjust the fuel mixture screw till you get the car to
run as smooth as possible and then plug the 02 back end. This should have
you really close to the sweet spot of idle. Be sure the three brass screws
are all screwed down.
As far as the WUR and the K Jet testing tool for fuel pressure. Follow the
instructions in the technical manual. That's the best. 
John Hervey
www.specialtauto.com

    

-----Original Message-----
From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
Todd Nelson
Sent: Thursday, June 29, 2006 8:43 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: Re: [DML] Is My Idle OK?

Thanks John,

I just recently replaced the O2 sensor, it's actually one of yours :-)  I 
bought it quite some time ago and finally got around to installing it.  I 
will take your advice and monitor the fuel spray from the injectors. 
Setting the fuel/air ratio is what I have been trying to do with little 
success.  What seems to be most troubling is I can never get the reading 
from the dwell meter to be steady.  It will usually hop somewhere between 35

and 50, sometimes in long swings sometimes in short swings say between 45 
and 50.  Is this normal?   Keep in mind this is all during one reading after

one setting change.  Do I just need to find that "sweet spot" for it to 
smooth out?

In regards to a possible faulty WUR/CPR, is this something that can be 
diagnosed with a K-Jet pressure testing tool?  Being in a "non-DeLorean" 
area means there are no other owners I can persuade into letting me try 
their parts for an hour or two.

I think I'm about 90% there with this car...

Thanks again,
Todd Nelson
1561, Vermont
http://www.rit.edu/~tan5732


----- Original Message ----- 
From: "John Hervey" <john@xxxxxxxxxxxxxxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>
Sent: Thursday, June 29, 2006 9:48 PM
Subject: RE: [DML] Is My Idle OK?


> Todd, See below:
>
> -----Original Message-----
> From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf 
> Of
> Todd Nelson
> Sent: Wednesday, June 28, 2006 4:49 PM
> To: dmcnews@xxxxxxxxxxxxxxx
> Subject: [DML] Is My Idle OK?
>
> List:
>
> The idle on my car seems to be a little rough, this could be due to it 
> using
> a very old mechanical fuel injection system or it could be something else.
>
> Todd, Have the injectors been cleaned or checked to see if they are all
> matched in pressure and bleed down.
>
> As this is the only DeLorean I've ever seen, much less driven, I'm not 
> sure
> what I should expect from the car as far as idle quality, and startup ease
> is concerned.
>
> Todd, I have had cars in the shop that Idle as smooth as any car should.
>
> When started, which can sometimes take a little help from the throttle
> pedal, the idle will fluctuate slightly, according to the in car 
> tachometer
> it doesn't appear to be too bad, maybe 50 RPM's.  However a short time 
> later
> the idle will sag maybe 150 RPM then pick itself up again, it will 
> continue
> in this cycle until I begin to drive it, at which time it may reappear.
>
> Todd, I would consider replacing the 02 sensor and re adjust the mixture
> screw.
>
>  Upon inspection of the engine when idling I will notice that it does seem
> to shake a little more than I would consider normal.  When sitting at a 
> stop
> light you can really feel the car rumble, I kind of like it, but if it's 
> not
> normal then I should do something about it.  When I bought the car I 
> noticed
> that the cap to the mixture screw was gone, assuming the mixture was set
> incorrectly I used the dwell meter approach connected to the diagnostic 
> plug
> to watch the readings while the car was at running temp.  Needless to say 
> it
> was off, not swinging between 45 degrees.  However I am unable to get it 
> to
> a steady swing, sometimes swinging between 45 and 50, sometimes 35 and 40,
> sometimes 40 and 50, I will notice this with the screw in the same place.
> The mixture screw hole is plugged during these readings, it just seems 
> more
> erratic than it should.  This leads me to think there is a vacuum leak of
> some kind in the system.  Although this seems unlikely since I have 
> replaced
> all of the engine vacuum hoses, intake O-rings, "air horn" paper and 
> rubber
> O-rings, cold start valve and tube O-rings, fuel distributor to mixture 
> unit
> O-ring and the paper gasket between the two halves of the mixture unit.
>
>
> Vacuum leaks normally are a steady problem as the vacuum is leaking.
>
>
> I have used the propane method for finding leaks, but it has proved
> unsuccessful.  What seems odd is as a test I removed the air cleaner while
> the engine was idling and "squirted" some propane directly in the intake 
> to
> see/hear the results, but surprisingly nothing happened, this didn't seem
> right to me.  I thought it could be the constant idle speed system
> regulating the idle, but this seems unlikely as I wouldn't suspect it to
> function that quickly.  At any rate I disabled the system by unplugging 
> the
> ISM and manually idling the car by using the "brass screws".  I 
> experienced
> the same results.  The only other running problem I've noticed is when
> manually working the throttle spool I can just barely hear a quiet pop 
> like
> a small backfire, just when holding at a constant high RPM.  When driving
> the car it's completely unnoticeable.  Other than that the car runs fine,
> acceleration seems good and power seems to be normal.  Then again, I've
> never driven another DeLorean.  Any thoughts?
>
> Little pop's in the intake are normally a sign of running to lean and a 
> WUR
> needs to be replaced.
>
> John Hervey
> www.specialtauto.com





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